Breast Abscesses and Masses

Breast masses are broadly classified as benign or malignant. Common causes of benign breast lesions include fibrocystic disease, fibroadenoma, intraductal papilloma, and abscess. Malignant breast disease encompasses many histologic types that include, but are not limited to, in situ ductal or lobular carcinoma, infiltrating ductal or lobular carcinoma, and inflammatory carcinoma. The main concern of many women presenting with a breast mass is the likelihood of cancer. Reassuringly, most breast masses are benign.

See Breast Lumps in Young Women: Diagnostic Approaches, a Critical Images slideshow, to help identify and manage palpable breast lumps in young women.

Breast infections are divided into lactational and non-lactational infections and puerperal versus nonpuerperal, depending on their association with pregnancy. The process may be confined to the skin overlying the breast, or it may result from an underlying lesion (eg, sebaceous cyst), as in hidradenitis suppurativa.[1, 2, 3, 4]

The mammary glands arise from a caudal section of the ectodermal tissue known as the “milk lines,” which extend along the anterior surface of the developing fetus from the axilla to the groin. During puberty, pituitary and ovarian hormonal influences stimulate female breast enlargement, primarily owing to accumulation of adipocytes. Each breast contains approximately 15-25 glandular units known as breast lobules, which are demarcated by Cooper ligaments. Each lobule is composed of a tubuloalveolar gland and adipose tissue. Each lobule drains into the lactiferous duct, which subsequently empties onto the surface of the nipple. Multiple lactiferous ducts converge to form one ampulla, which traverses the nipple to open at the apex.[5]

Below the nipple surface, lactiferous ducts form large dilations called lactiferous sinuses, which act as milk reservoirs during lactation.[6] When the lactiferous duct lining undergoes epidermalization, keratin production may cause plugging of the duct, resulting in abscess formation.[7, 8] This may explain the high recurrence rate (an estimated 39%-50%) of breast abscesses in patients treated with standard incision and drainage, as this technique does not address the basic mechanism by which breast abscesses are thought to occur.

Postpartum mastitis is a localized cellulitis caused by bacterial invasion through an irritated or fissured nipple. It typically occurs after the second postpartum week and may be precipitated by milk stasis.[9] There is usually a history of a cracked nipple or skin abrasion or failure to clean nipples after breastfeeding.[10] Sleeping position may also affect the progression of mastitis to breast abscess.[10] Staphylococcus aureus is the most common organism responsible, but Staphylococcus epidermidis and streptococci are occasionally isolated. Drainage of milk from the affected segment should be encouraged and is best achieved by continued breastfeeding or use of a breast pump.[3, 8, 4]

Nonlactating infections may be divided into central (periareolar) and peripheral breast lesions. Periareolar infections consist of active inflammation around nondilated subareolar breast ducts—a condition termed periductal mastitis. Peripheral nonlactating breast abscesses are less common than periareolar abscesses and are often associated with an underlying condition such as diabetes, rheumatoid arthritis, steroid treatment, granulomatous lobular mastitis, trauma, and smoking.[1, 11, 12] Primary skin infections of the breast (cellulitis or abscess) most commonly affect the skin of the lower half of the breast and often recur in women who are overweight, have large breasts, or have poor personal hygiene.[3]

Breast masses can involve any of the tissues that make up the breast, including overlying skin, ducts, lobules, and connective tissues. Fibrocystic disease, the most common breast mass in women, is found in 60%-90% of breasts during routine autopsy. Fibroadenoma, the most common benign tumor, typically affects women aged 30 years or younger and accounts for 91% of all solid breast masses in females younger than 19 years.[5] Infiltrating ductal carcinoma is the most common malignant tumor; however, inflammatory carcinoma is the most aggressive and carries the worst prognosis. Mammary Paget disease, or adenocarcinoma of the nipple epidermis, is relatively rare but may be misdiagnosed as a benign dermatosis if care is not taken.[13, 14]

Frequency

Statistics provided refer to populations in the United States.

After skin cancer, breast cancer is the most commonly diagnosed cancer in women, accounting for roughly 1 in 4 cancers diagnosed and affecting 12.4% of women during their lifetime.[15]

Breast infections occur in as many as 10%-33% of lactating women.[16, 17]

Lactational mastitis is seen in approximately 2%-3% of lactating women,[6, 18, 4] and breast abscess may develop in 5%-11% of women with mastitis.[18, 4]

Mortality/Morbidity

Breast mass

Morbidity and mortality depends on etiology (benign vs malignant) and stage of malignant lesions.

Approximately 2.1%-3.6% of women die of breast cancer. In 2009, approximately 40,170 women were expected to die from breast cancer,[15] remaining stable at 40,610 in 2017, just behind lung and colon cancer.

Despite significant differences in sociodemographic and clinical characteristics, overall and disease-free survival rates are similar for men and women with breast cancer.[19, 20]

Associated morbidity may include scarring, disfigurement, lymphedema, and psychologic stress.

Breast abscess

Recurrent or chronic infections, pain, and scarring are causes of morbidity.

Mastitis is usually seen in lactating women, but the presence in a nonlactating woman should spur evaluation for an inflammatory carcinoma, newly onset diabetes, infection with​Mycobacterium tuberculosis, and other idiopathic causes.[3, 12]

Abscess formation complicates postpartum mastitis in fewer than 10% of cases.

Neonatal mastitis usually occurs in term or near-term infants, is twice as common in females, and progresses to development of a breast abscess in approximately 50% of cases.[21, 22, 5]

Development of mastitis has been correlated with an increased risk of developing breast cancer.[23, 24]

Race

While white women have a higher incidence of breast cancer than African American women after age 40 years, African American women have a higher incidence of early breast cancer (before age 40 years) and are more likely to die of breast cancer at every age.[25]

African-American women have been variably reported to have an increased incidence of developing a primary breast abscess.[26, 27]

Sex

Approximately 99% of breast cancers are found in women.

Up to 1% of breast cancers occur in men, but numbers have been increasing.[19, 28] Men with changes in breast size should undergo as aggressive of a diagnostic workup as women.[21, 22, 29, 30] Because of the high rate of hormone estrogen receptor positivity in male patients, hormonal therapy is a treatment mainstay for many men.

Since the indications and outcomes of biopsies in trans women have been observed to be similar to those in cis women, it seems reasonable to follow breast care guidelines as developed for cis women.[31]

Age

Lumps or breast masses are the most frequent breast pathology in adolescence, but malignancy is extremely rare in this age group.[32] Fibroadenoma, a benign condition, is the most common cause of breast mass in women younger than 35 years.[5]

In 2017, women aged 40 years or older accounted for nearly 96% of new breast cancer diagnoses and 98% of breast cancer deaths.

The median age at breast cancer diagnosis is 62 years.

Breast infections most commonly affect women aged 18-50 years.[3]

Nonpuerperal breast masses encompass a wider range of ages, from the late second to eighth decade of life. Peak incidence is often in the fourth decade of life. Ninety-five percent of these infections occur in women.[8]

Puerperal breast abscesses and mastitis are commonly found in women of childbearing age (mean age of 32 years).[1]

Non-neonatal pediatric breast abscess bacteriology is similar to other skin abscesses.[33]

Access to care

Women who reside in rural settings may be more likely to present with a more advanced cancer stage than women in urban settings. This may partly result from the availability of and access to effective screening tools and primary care.[34]

Breast mass: Prognosis varies from excellent in patients with a fibroadenoma to poor in those with inflammatory breast cancer. Influencing factors include tumor size, histology, nodal involvement, distant metastases, and comorbid conditions.

Breast abscess: Unfortunately, the recurrence rate of breast abscess is high (39%-50%) when treated with standard incision and drainage, and studies have shown even higher recurrence rates in women undergoing fine-needle aspiration.[35] Nonpuerperal abscesses recur more frequently, especially when associated with non-staphylococcal species (>50% recurrence rate).[8] Studies of patients with fistulectomy show lower recurrence rates.

Mastitis: Most patients experience resolution within 2 to 3 weeks. All patients with symptoms that have not resolved within 5 weeks should be evaluated for resistant infection or malignancy.

Educate women who are lactating on nipple hygiene because cracking and abrasions of the skin increase risk of infection.

For excellent patient education resources, visit eMedicineHealth's Women's Health Center and Cancer Center. Also, see eMedicineHealth's patient education articles Breast Infection, Breast Lumps and Pain, Breast Self-Exam, and Breast Cancer.

Breast mass

The following may be seen in those with a breast mass:

• Palpable mass (typically unilateral)

• Family history of breast disease (malignant or benign)

• Early menarche (< 12 years) and obstetrical parity (nulliparity)

• Late menopause (age >55 years)

• Associated symptoms of pain, nipple discharge, and skin changes (eg, dimpling or inflammation, nipple inversion)

• Length of time present, speed of growth

• Nipple itchiness without lump (Paget disease)[13]

Mastitis

The following may be seen in those with mastitis:

• Localized breast erythema, warmth, swelling, and pain
• May have fever, chills, or rigor
• Lactation history including difficulty with breastfeeding, breast engorgement, or chafed nipples ^[9]

Breast abscess

The following may be seen in those with a breast abscess:

• Localized breast edema, erythema, warmth, and pain ^[4]
• Any history of prior breast infection
• Associated symptoms of fever, nausea, vomiting, and spontaneous drainage from the mass or nipple ^{[9, 4]}
• Lactation history (consider if weaning or returning to work)
• If not lactating, consider diabetes (polyuria, polydipsia, frequent infections, weight change)
• Surgical breast intervention within 8 weeks ^[36]
• Smoking history

Perform a thorough breast examination in any patient presenting with a breast complaint and in any older woman presenting with unexplained weight loss, anorexia, or bone pain.

Breast mass

Examine the patient with a breast mass for the following:

• Firm mass of variable shape and size

• Observe whether fixed or mobile

• Fifty percent of masses found in the upper outer quadrant of the breast

• May have associated pain with palpation (most are painless)

• Nipple discharge, inversion, changes, or asymmetry

• Skin retraction or tethering

• Axillary lymphadenopathy

• Skin changes - Inflammatory (ie, peau d'orange) or erythematous scaly lesions of the areola (ie, Paget disease)[13]

• Pay special attention to associated upper-extremity neurologic motor or sensory abnormalities, as these may herald invasion of the brachial plexus—an indication for emergent radiation therapy

Mastitis

Examine the patient with suspected mastitis for the following:

• Localized breast erythema, warmth, induration, swelling, and tenderness

• May have associated fever

Breast abscess

Examine the patient with a suspected breast abscess for the following:

• Localized breast erythema, warmth, induration, edema, and tenderness

• Most frequently areolar or periareolar (may also be peripheral)

• Fluctuance, although swelling may limit ability to palpate a mass

• May have associated fever or axillary lymphadenopathy

• Nipple discharge or inversion

Malignant

Risk factors for females include the following:

• Age older than 40 years
• Family history of a first-degree relative with breast cancer
• Menarche before age 12 years
• Menopause after age 55 years
• Nulliparity
• First pregnancy after age 30 years
• Therapeutic radiation over chest before age 30 years
• Prediagnosis hormone replacement therapy remains controversial ^[37]
• A history of smoking tobacco products for more than 15 years ^[38]
• BRCA1 and BRCA2 mutations (responsible for approximately 5% of all breast cancers; inherited in an autosomal dominant fashion; women with mutations in either of these genes have a lifetime risk of breast cancer of 60%-85% and a lifetime risk of ovarian cancer of 15%-40%) ^[39]
• Paget disease of the breast ^[40]

Risk factors for males are as follows[41]

• BRCA1 and BRCA2 mutations
• Klinefelter syndrome: 20- to 50-fold greater lifetime risk
• Cowden syndrome
• Hormonal imbalance and increased estrogen levels, including liver disease and testicular abnormalities
• Environmental exposures, including to ionizing radiation, electromagnetic radiation, polycyclic aromatic hydrocarbons, alcohol, and red meat, have been studied in relation to male breast cancer, but none has convincingly been found to be associated with incidence across studies.

Exercise has been shown to decrease the risk of breast cancer in women at high risk for developing a malignancy. However, further studies are needed to verify this association and its relationship to preventing breast cancer in women on tamoxifen therapy (standard treatment for preventing breast cancer recurrence).[38]

Alcohol consumption has not been shown to increase the risk of developing breast cancer.[38]

Benign

Developmental breast lesions

Prepubertal and peripubertal developmental breast lesions may include abnormalities of embryology and gynecomastia.

Abnormalities of embryology include polythelia (accessory nipples) and polymastia (supernumerary breasts).

Gynecomastia is characterized by excessive development of breast tissues in males. It can be physiologic or pathologic in teens.

Neonatal breast hypertrophy is a common transient condition that results from elevation of maternal hormones, seen in up to 90% of all newborns.

Non-developmental breast lesions

Fibrocystic changes

Breast lobules may dilate and form cysts of varying sizes, due to hormonal changes in the menstrual cycle. Cysts are found in about 1 in 3 women aged 35-50 years.[15] Rupturing of the cysts can cause scarring and inflammation that leads to fibrotic changes, which feel rubbery, firm, or hard.

Hyperplasia

Hyperplasia is caused by an overgrowth of cells that line the ducts or lobules. About 1 in 4 women have mild or usual hyperplasia.[15] About 1 in 25 women have atypical hyperplasia (associated with an increased risk of malignancy).[15]

Adenosis

An increase in the number of glands.

Fibroadenoma[6, 16, 42]

Fibroadenoma is the most common cause of breast mass in women younger than 35 years and comprises 91% of all solid breast masses in females younger than 19 years.[42] These arise from the terminal duct lobular unit and appear clinically as singular, firm, rubbery, smooth, mobile, painless masses ranging in size from 1-5 cm. They may grow to a large size, thereby affecting the contours of the overlying skin and overall shape of the breast. Ultrasonography reveals a well-defined hypoechoic homogeneous mass 1-20 cm in diameter.[16, 42] Fibroadenomas appear as multiple masses in 10%-15% of patients.[16]

Phyllodes tumor[6, 42]

Phyllodes tumor is also known as cystosarcoma phyllodes or giant fibroadenoma. Although generally benign, a malignant variant occurs in 10% of cases. Incidence is highest among women aged 40 to 60 years. Phyllodes tumor is also the most common primary breast malignancy in adolescents.[42] The most common presentation is that of a large (average 5 cm), solitary, firm, breast nodule. Ultrasonographic findings of the mass may appear identical to those of a fibroadenoma with well-circumscribed borders and small cysts.[42]

Papillary adenoma of the nipple[6]

Papillary adenoma is also known as erosive adenomatosis of the nipple, adenoma of the nipple, florid papillomatosis of the nipple, and subareolar duct papillomatosis of the nipple. This is believed to arise from terminal lactiferous ducts. Incidence is highest among women aged 40 to 50 years. It commonly presents with unilateral serous or bloody nipple discharge that increases before menses.

Vascular lesions

Vascular lesions are usually benign. The most common form is hemangioma. Surgical excision may be required.[42]

Infectious

Breast abscess

Puerperal breast abscesses most often contain S aureus and streptococcal species. Methicillin-resistant S aureus (MRSA) has become increasingly common.[26] The overall rate of breastfeeding cessation among patients with breast abscess was 41% in a US cohort and did not differ between MRSA and MSSA infections.[43] In a US cohort, 81% of S aureus–confirmed cultures were MRSA pulsed-field type USA 300–0114.[43] Nonpuerperal abscesses typically contain mixed flora (S aureus, streptococcal species) and anaerobes.[3] Diabetes is strongly associated with incidence and clinical outcomes of breast abscesses in nonlactating women. One study demonstrated a 72% prevalence of diabetes in women with nonpuerperal abscesses.[44] Cigarette smoking is a debated risk factor but has been shown to have a strong association with development of nonpuerperal mastitis.[3, 26, 27, 45, 46] Primary breast abscess has also been reported to be more common in African Americans[27] and those with obesity,[27] and a possible association with inadequate vitamin A supplementation has also been described.[8] Nipple piercing has been associated with increased risk of developing subareolar breast abscess.[46]

Mastitis

Mastitis occurs in up to 33% of lactating women, with its highest incidence within 6 weeks postpartum or while weaning breastfeeding.[18, 47, 48]  Periductal mastitis comprises 3%-4% of all benign lesions of the breast.[6] It may be associated with milk stasis caused by ineffective positioning of the baby, limited feeding, or restricted feeding.[9] Of infective mastitis cases, S aureus is the most common cause. Streptococci, enterococci, S epidermidis, Peptostreptococcus species, Prevotella species, and Escherichia coli are less common causes. True fungal mastitis is rare and should prompt evaluation for coexisting diabetes mellitus. In infants, infections with Shigella, E coli, and Klebsiella species have been reported.[22] Mastitis that is refractory to appropriate treatment should prompt evaluation for tuberculous mastitis.[12]

Potential complications are as follows:

• Breast mass - Chronic pain, scarring or disfigurement, metastases, postsurgical complications (eg, ipsilateral lymphedema), and death
• Mastitis - Breast abscess formation in less than 10% of cases
• Breast abscess - Recurrent infection, scarring, loss of breast size, and noticeable breast asymmetry
• Chronic breast abscess - Mammary duct fistulization, resection of the nipple-areolar complex ^[11]

In patients suspected of having a breast abscess, a CBC count with differential may be helpful. Send an aerobic and anaerobic culture during surgical drainage.

Ultrasonography is used to distinguish solid from cystic structures and to direct needle aspiration for abscess drainage. Simple cysts are seen on sonograms as round or oval with sharply defined margins and posterior acoustic enhancement. Complex cysts are characterized by a significant solid component, septations, lobulations, varied wall thickness, and the presence of internal debris. Abscesses usually appear as ill-defined masses with central hypoechoic areas and may display internal septations, debris, posterior enhancement, eccentrically thickened walls, and increased Doppler flow in the walls and surrounding tissue with lack of internal color Doppler flow.[8, 36, 42, 49, 50] The addition of elastography and color Doppler ultrasonography to B-mode ultrasonography has been reported to increase the positive predictive value (PPV) of screening ultrasonography in women with dense breasts (from 8.9% to 23.2%; P< .001]) while reducing the number of false-positive findings without missing cancers.[51, 52] Thus, ultrasonography may be particularly useful in younger patients (< 40 years).[53] In addition, ultrasound-guided biopsy has been shown to be safe and effective.[54]

Contrast-enhanced ultrasonography has also been found to be helpful in distinguishing benign from malignant breast masses. This modality has been shown to be 86% sensitive and 79% specific for differentiating between the two types of masses.[55] For more information, see Breast Cancer, Ultrasonography.

It should be noted that although bedside ultrasound performed in the emergency department (ED) by trained emergency medicine providers (rather than by radiology) may effectively identify an abscess,[56] patient selection is important. In one study, 40% of ED bedside studies were incomplete/inadequate, and 21% of cancers were not identified.[57]

Various types of breast masses are shown in the images below.

Schedule an outpatient mammography to further characterize the suspected breast mass. The sensitivity of mammography ranges from 74%-95%, and specificity ranges from 89%-99%.[58, 59] In a meta-analysis of more than 8.5 million patients, the AUC of mammography for breast cancer screening was 0.95, the overall sensitivity was 0.81, and the overall specificity was 0.96.[60] A subgroup analysis of dense-breast populations showed that the combined sensitivity and specificity of mammography was 0.74 and 0.93, respectively.[60]

Early detection with screening mammography significantly reduces breast cancer–related mortality by 20% to 40%.[61] Annual screening mammography of women aged 40-84 years prevents more deaths due to breast cancer than biennial screening of women aged 50 to 74 years.[61] Currently, supplemental screening with ultrasonography or MRI is recommended in addition to mammography.[61] The American Cancer Society recommends annual screening mammography and supplemental screening MRI in women with an estimated lifetime risk of breast cancer of 20%, BRCA mutation carriers, first-degree relatives of BRCA mutation carriers who remain untested, women with a history of mediastinal irradiation aged 10-30 years, and women with certain genetic syndromes.[61] With aggressive public screening, the incidence of large breast tumors may be decreasing.[62] However, with increased screening comes the risk of overdiagnosis.

Approximately 5%-10% of screening examinations are interpreted as abnormal, but 90% of women with abnormal results do not have breast cancer.[58, 59] For instance, the Canadian National Breast Screening Study concluded that approximately 30% of invasive screen-detected breast cancers in women aged 40 to 49 years and 20% of those screen-detected in women aged 50 to 59 years were overdiagnosed.[63] Moreover, a subsequent meta-analysis reported no significant effect on either breast cancer mortality or all-cause mortality when breast cancer screening was extended to women aged 40 to 49 years, but the rates of overdiagnosis were estimated to be 32% at 5 years following cessation of screening and 48% at 20 years following cessation.[64] For these reasons (and others), current guidelines do not recommend extending routine mammography screening to younger age groups.[64] However, when screening women with dense breasts, the addition of bedside ultrasonography may be useful. In a cohort of 66,680 women undergoing physician-performed ultrasonography in addition to mammography, the sensitivity of mammography with ultrasonography rose from 61.5% to 81.3%.[65]

Racial disparities in utilization of screening mammography are evident in black and Hispanic populations in the United States.[66] Further studies are needed to understand reasons for disparities, trends over time, and the effectiveness of interventions targeting these disparities.[66]

For more information, see Breast, Benign Calcifications, Breast, Fibroadenoma, Breast, Nipple Discharge Evaluation, and Breast Cancer, Mammography.

Supplemental ultrasonography improves cancer detection in screening of women at average risk. When comparing screening with mammography alone versus mammography plus physician–performed ultrasonography in average-risk women, the overall sensitivity of mammography alone was 86.6% (non-dense breast) and 61.5% (dense breast) versus 95% (non-dense breast) and 81.3% (dense breast) for mammography with ultrasonography.[65] Adjunctive ultrasonography increased the recall rate from 10.5 to 16.5 per 1000 women screened and increased the biopsy rate from 6.3 to 9.3 per 1000 women screened.[65] The positive predictive value of biopsy was 55.5% for mammography alone and 43.3 for combined mammography plus ultrasonography.[65]

Computer-aided digital breast tomosynthesis is a new imaging modality that has shown some promise as an additional (or even sole) screening tool for breast cancer. Current studies of computer-aided digital breast tomosynthesis show sensitivity of detecting masses and microcalcifications ranging between 85% and 89%. Its utility in detecting masses in dense breast tissue is still a debated topic. Current US guidelines have recommended against its routine use.[67]

MRI may also be helpful in select cases. On diffusion-weighted imaging (DWI), profoundly low apparent diffusion coefficient values were a distinguishing sign of breast abscess due to necrotic breast cancer.[68]

Various breast masses are shown in the mammograms below.

Breast abscesses may be drained with incision and drainage (versus ultrasound-guided needle aspiration and irrigation). Historically, incision and drainage was considered the standard of care for abscesses. Although this method has a lower reoccurrence rate, it is more invasive than needle aspiration and frequently results in scarring with structural damage and poor cosmetic outcomes.[69] Fine-needle aspiration should be considered first-line therapy for abscesses smaller than 5 cm owing to its lower risks, followed by incision and drainage if recurrence occurs.[4] Surgical excision may be required for infected or obstructed lactiferous ducts and provides a lower rate of recurrence for nonpuerperal abscess and mastitis.[70, 8]

Ultrasound-guided needle aspirations are more successful on abscesses smaller than 3 cm and on puerperal abscesses.[71, 72, 73, 8] Loculations are associated with failure of resolution with aspiration, regardless of abscess volume.[74] Nonpuerperal abscesses have a higher rate of recurrence and often require multiple drainage attempts.[8] Regardless of the underlying organism, the need for repeat aspiration is common in patients treated with aspiration versus incision and drainage.[75] In a US cohort of 54 abscess cases treated with needle-guided aspiration, the median number of drainage procedures was 2 (interquartile range, 1.0-4.0), with 24% requiring 5 or more drainage procedures.[43]

Vacuum-assisted biopsy is a viable option for the management of lactational breast abscesses and has been associated with a shorter healing time than simple needle aspiration.[76] Furthermore, percutaneous catheter drainage may be considered for larger abscesses.[4, 77]

Ultrasonographic elastography with virtual touch tissue quantification (VTQ) is used to characterize breast lesions and to analyze the stiffness of glandular and subcutaneous fatty tissue in benign and malignant lesions.[78, 79] Acoustic radiation force impulse imaging is used to measure shear wave velocity (SWV), which reflects the stiffness of tissue. Tissue stiffness is measured within the lesion (internal SWV-SWVi) , in the boundary zone (SWVb), in normal‐appearing glandular tissue (SWVg), and in subcutaneous fatty tissue (SWVf). SWVs inside and at the edge of a breast mass are important for determining if they are benign or malignant. All types of SWVs were significantly higher in the malignant group than the benign group (P< 0.05).

Breast mass

Definitive diagnosis of the etiology can only be made by pathologic examination and is not an emergency. Timely follow-up care, including mammography and involvement of primary physician and surgeon, is essential.

Finding a breast mass can be stressful for patients; provide reassurance that not all breast masses are malignant.

Mastitis

For detailed therapy, see Mastitis Empiric Therapy and Mastitis Organism-Specific Therapy.

In general, mastitis is treated with antibiotic therapy for 10 to 14 days, warm or cold compresses, and (for patients with lactational mastitis) continued breast emptying via breastfeeding or breast pumping every 2 hours or when engorged.

Antibiotic therapy with continued breast emptying has been shown to be superior to breast emptying alone for resolving symptoms, decreasing recurrence rate, and decreasing the risk of abscess development.[1, 9] The addition of appropriate antibiotic administration may relieve symptoms in 2.1 days, as compared with 4.2 days for supportive care or 6.7 days if no action is taken.[9] Breast infections are frequently polymicrobial with a wide variety of organisms isolated, suggesting the need for broad spectrum coverage until culture results become available.[80]  In breastfeeding mothers, use beta-lactamase stable penicillin. Other choices include dicloxacillin 500 mg orally 4 times daily or cephalexin 500 mg orally 4 times daily for 10 to 14 days. Instruct patients who are lactating that continued breastfeeding from the affected breast is not harmful to the baby. For nonpuerperal mastitis, use clindamycin 600 mg intravenously every 8 hours or 300 mg orally every 6 hours, or amoxicillin/clavulanate 500 mg orally 3 times daily.[81] If a breast abscess is suspected in a nursing mother, the affected breast should not be used to nurse the baby owing to the risk of passing infection to the baby.[4]

Initial antibiotic selection for those with peri-prosthetic infections should be similar to those for patients without breast implants.[82, 83]

Corynebacterial infection is associated with longer treatment courses and an increased recurrence rate of complicated mastitis.[84]

Breast abscess

Historically, incision and drainage was considered the standard of care for abscesses. Although this method yields a lower recurrence rate, it is more invasive than needle aspiration and frequently results in scarring with structural damage and poor cosmetic outcomes.[69] Fine-needle aspiration should be considered first-line therapy for abscesses smaller than 5 cm owing to its lower risks, followed by incision and drainage if recurrence occurs.[4] Although success has been reported with oral antistaphylococcal antibiotics and serial aspiration,[85] surgical excision may be required for infected or obstructed lactiferous ducts and provides a lower rate of recurrence for nonpuerperal abscess and mastitis.[70, 8]

In pediatric patients, treatment modality was not associated with persistent disease.[86] A trial of antibiotics alone may be considered to minimize the risk of breast bud damage and adverse cosmetic outcomes with invasive intervention.[86]

For persistent lesions, treatment options may include ultrasound-guided needle aspiration,[20] percutaneous drainage catheter,[77]  and/or surgical drainage. Ultrasound-guided needle aspirations are more successful for abscesses smaller than 3 cm and for puerperal abscesses.[8, 71, 72, 73, 87] Loculations are associated with failure of resolution with aspiration, regardless of abscess volume.[74] Nonpuerperal abscesses have a higher recurrence rate and often require multiple drainage attempts.[8] Regardless of the underlying organism, the need for repeat aspiration is common in patients treated with aspiration versus incision and drainage.[75] In a US cohort of 54 abscess cases treated with needle-guided aspiration, the median number of drainage procedures was 2 (interquartile range, 1.0-4.0), with 24% requiring 5 or more drainage procedures.[43]

The vacuum-assisted breast biopsy (VABB) system is a viable option for the management of lactational breast abscesses and has been associated with a shorter healing time than simple needle aspiration.[76, 88] ​ Furthermore, percutaneous catheter drainage may be considered for larger abscesses.[4, 77]

In one study, there was no difference in clinical characteristics between breast abscesses infected by methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-susceptible Staphylococcus aureus (MSSA), and the authors recommended no change in interventional treatment based on a positive MRSA culture result.[89]

Patients with breast masses require a general surgeon for definitive treatment. Immediate consultation in the ED is not mandatory, but it may help facilitate faster follow-up care once patients are discharged from the hospital.

Patients with mastitis unresolved by a single course of correct antibiotics need urgent referral to a surgical breast specialist.[11] Similarly, refer patients with breast abscesses for surveillance of complications and possible recurrent breast abscesses.

Lactation nurses can also be of great help in advising about nipple hygiene and hand washing and preventing engorgement of the breast.

Breast mass screening

For breast cancer screening guidelines, see the Guidelines section.

Future studies are needed to determine the efficacy and effectiveness of breast cancer screening with mammography in women aged 40 to 49 years. Some research shows a modest decrease in breast cancer mortality when women in this age group are screened; however, further research is needed to compare risks of overdiagnosis (one study suggests 1 in 424 women screened would be overdiagnosed) versus potential benefits of screening.[35, 90]

Similar rates of cancer detection have been found between short-term interval follow-up (SIFU) and return to annual screening (RTAS) after benign breast biopsy with no significant differences in stage, tumor size, or nodal status, although the present study was limited by sample size.[91] Additionally, positive predictive values have been reported not to change in patients receiving 6 and 12-month re-biopsy follow-up.[92] These findings suggest that patients with benign radiologic-pathologic-concordant percutaneous breast biopsy results could return to annual screening.

Mastitis

In addition to therapeutic breast emptying (if indicated), antibiotic therapy, and warm or cold compresses, emerging evidence suggests that therapeutic administration of lactobacilli strains that are naturally occurring in breast milk may be of therapeutic benefit for the management of infectious mastitis during lactation.[9, 93]

Mastitis that is refractory to standard treatment (see above) should prompt further workup to rule out uncommon infectious etiologies, granulomatous diseases, and/or idiopathic causes.[12]

Recurrent periductal mastitis may require combined total excision of the affected duct and the fistulous tract with encouraged smoking cessation (if applicable).[94]

Treatment of idiopathic granulomatous mastitis usually involves corticosteroids and methotrexate, with or without surgery.

Consider admitting patients with large or complex breast abscesses for pain management, parenteral antibiotic therapy, and definitive management. Admit patients with sepsis due to mastitis. Consider diabetic ketoacidosis in patients with nonpuerperal breast abscess.

Treatment may include incision and drainage, fine-needle aspiration, vacuum-assisted aspiration, and fistulectomy in the operating room. The wound can be left to close by secondary intention or with simple sutures over a drain.[4, 95]  Cultures of the drained fluid should be obtained at this time and sent to determine antimicrobial susceptibility.[4]

Prescribe pain medication to patients with a breast abscess as necessary. NSAIDs, such as ibuprofen, are preferred because they are not transferred through breastmilk. Preparations combining acetaminophen with codeine, oxycodone, or hydrocodone may be used depending on the level of discomfort but should be avoided in breastfeeding mothers with concern for sedation and respiratory depression in the infant.

Prescribe parenteral narcotics for pain control while awaiting definitive surgical therapy.

Continue antibiotic therapy for 14 days after drainage.

Transfer typically is not necessary for patients with breast mass, abscess, or mastitis.

Multiple guidelines are available pertaining to breast cancer screening. The three most cited include those by the American College of Physicians (2015), the American Cancer Society (2015), and the United States Preventive Services Task Force (2016).

American College of Physicians (ACP) screening guidelines recommend the following[96] :

• Mammography every 2 years from age 50-74 years
• For women aged 40-49 years, guidelines advocate an individualized approach in which clinicians should base decisions on the potential benefits and harms of mammography, the woman's preferences, and her breast cancer risk profile
• Current evidence recommends against breast cancer screening with mammography in women younger than 40 years, women older than 75 years, and women with a serious medical condition who have a life expectancy of less than 10 years. However, physicians and patients should discuss the risks and benefits of mammography based on the patient’s wishes and other associated breast cancer risks.

American Cancer Society (ACS) screening guidelines recommend the following[97] :

• For women aged 40-44 years, the choice to begin annual breast cancer screening with mammography should be based on the potential risks/benefits and patient’s wishes.
• For women aged 45-54 years, mammography should be completed annually.
• For women aged 55 years and older, mammography should be completed every 2 years and continued until life expectancy falls below 10 years.

The US Preventive Services Task Force (USPSTF) screening guidelines recommend the following[98] :

• Mammography every 2 years between age 50 and 74 years
• For women aged 40-49 years, guidelines advocate an individualized approach in which clinicians should base decisions on the potential benefits and harms of mammography, the woman's preferences, and her breast cancer risk profile
• The USPSTF has found insufficient evidence to make a recommendation about breast cancer screening in women younger than 40 years or older than 75 years.

The above guidelines share the following recommendations:

• No clear recommendations for breast self-examination
• No clear recommendation for clinical breast examination

ACP and ACS guidelines do not recommend the use of MRI or digital breast tomosynthesis for the purposes of breast cancer screening. USPSTF has found insufficient evidence to provide a recommendation about either of these breast cancer screening modalities.

French College of Gynecologists and Obstetricians (CNGOF) screening guidelines recommend the following[99] :

• Screening with breast ultrasonography in combination with mammography is needed to investigate a clinical breast mass (grade B), colored single-pore breast nipple discharge (grade C), or mastitis (grade C).
• The BI-RADS system is recommended for describing and classifying abnormal breast imaging findings.
• For a breast abscess, a percutaneous biopsy is recommended in the case of a mass or persistent symptoms (grade C).
• For mastalgia, when breast imaging findings are normal, no MRI or breast biopsy is recommended (grade C). Percutaneous biopsy is recommended for a BI-RADS category 4-5 mass (grade B).
• For persistent erythematous nipple or atypical eczema lesions, a nipple biopsy is recommended (grade C).
• For distortion and asymmetry, a vacuum core-needle biopsy is recommended owing to the risk of underestimation by simple core-needle biopsy (grade C).
• For BI-RADS category 4-5 microcalcifications without any ultrasound signal, a minimum 11-G vacuum core-needle biopsy is recommended (grade B). In the absence of microcalcifications on radiography cores, additional samples are recommended (grade B).
• For atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, flat epithelial atypia, radial scar and mucocele with atypia, surgical excision is commonly recommended (grade C). Expectant management is feasible after multidisciplinary consensus. For these lesions, when excision margins are not clear, no new excision is recommended except for LCIS characterized as pleomorphic or with necrosis (grade C).
• For grade 1 phyllodes tumor, surgical resection with clear margins is recommended.
• For grade 2 phyllodes tumor, 10-mm margins are recommended (grade C).
• For papillary breast lesions without atypia, complete disappearance of the radiological signal is recommended (grade C).
• For papillary breast lesions with atypia, complete surgical excision is recommended (grade C).

The goals of pharmacotherapy are to reduce morbidity, prevent complications and eradicate the infection.

Empiric therapy should have activity against S aureus, a common pathogen of primary breast abscess. Other pathogens may include methicillin-resistant S aureus (MRSA), Streptococcus pyogenes, E coli, Bacteroides species, Corynebacterium species, coagulase-negative staphylococci, Pseudomonasaeruginosa, Proteusmirabilis, and anaerobes. Therapy should be tailored to results of cultures and susceptibilities, if applicable.

Recurrent breast abscesses have an increased risk for mixed flora and anaerobic pathogens.

Antibiotics should be continued for 10 to 14 days.

Outpatient therapy for non-severe infection without MRSA risk: dicloxacillin or cephalexin or amoxicillin-clavulanate

Outpatient therapy in patients with hypersensitivity to beta-lactams: clarithromycin or doxycycline

Outpatient therapy for non-severe infection with MRSA risk: trimethoprim-sulfamethoxazole or clindamycin. Trimethoprim-sulfamethoxazole may be associated with an increased risk of allergic reactions relative to other MRSA-directed therapies.[100, 101]

Inpatient therapy for severe infection without risk of MRSA: nafcillin or oxacillin or ampicillin-sulbactam

Inpatient therapy for severe infection with risk of MRSA or in patients with beta-lactam allergy: clindamycin or vancomycin or linezolid or tigecycline or daptomycin

Emerging therapies include ceftaroline or dalbavancin or delafloxacin or oritavancin. These drugs have been approved by the FDA for treatment of soft-tissue infections but have not yet been studied specifically for treating breast infections.

Class Summary

Antibacterial therapy must cover all likely pathogens in the context of the clinical setting.

Dicloxacillin

Outpatient therapy

Drug of choice (DOC) for mastitis. Bactericidal antibiotic that inhibits cell wall synthesis. Used to treat infections caused by penicillinase-­producing staphylococci. May be used to initiate therapy when a staphylococcal infection is suspected.

Amoxicillin/clavulanate (Augmentin, Augmentin ES-600, Augmentin XR)

Outpatient therapy

Amoxicillin binds to penicillin­-binding proteins, thus inhibiting final transpeptidation step of peptidoglycan synthesis in bacterial cell walls; addition of clavulanate inhibits beta-­lactamase–producing bacteria, allowing amoxicillin extended spectrum of action

It is a semisynthetic antibiotic with a broad spectrum of bactericidal activity, covering both gram-­negative and gram-­positive microorganisms.

Nafcillin

Inpatient therapy

DOC for puerperal breast abscess. Used to treat infections caused by penicillinase-­producing staphylococci. Used to initiate therapy when a penicillin G–resistant staphylococcal infection is suspected.

Because of occasional occurrence of thrombophlebitis associated with parenteral route (particularly in elderly persons), administer parenterally only for a short term (24-­48 hours) and change to a PO equivalent, if clinically possible.

Oxacillin (Bactocill)

Inpatient therapy

Bactericidal antibiotic that inhibits cell wall synthesis. Used in the treatment of infections caused by penicillinase­-producing staphylococci. May be used to initiate therapy when a staphylococcal infection is suspected.

Ampicillin/sulbactam (Unasyn)

Inpatient therapy

Alternative DOC for nonpuerperal breast abscess. Drug combination that utilizes a beta-­lactamase inhibitor with ampicillin.

Covers skin, enteric flora, and anaerobes. Not ideal for nosocomial pathogens.

Cephalexin (Keflex, Daxbia)

Outpatient therapy

Cephalexin is a first-generation cephalosporin that binds to penicillin-binding proteins, therefore inhibiting bacterial cell wall synthesis. May be used to initiate therapy when a staphylococcal infection is suspected. Lacks coverage of gram-negative pathogens.

Ceftaroline (Teflaro)

Emerging therapy

Beta­-lactam cephalosporin with activity against aerobic and anaerobic gram-­positive and aerobic gram-­negative bacteria.

Demonstrates activity in vivo against resistant MRSA strains and in vitro against vancomycin-­resistant and linezolid­-resistant S aureus.

Pregnancy Category B, effects unknown. Unknown if secreted in breast milk; use caution if breastfeeding.

Delafloxacin (Baxdela)

Emerging treatment

Fluoroquinolone antibiotic that inhibits enzymes required for bacterial synthesis.

In vitro activity against S aureus (including MRSA), Streptococcus species, E coli, K pneumoniae, E cloacae, and P aeruginosa.

Limited data regarding use in pregnancy and lactation.

Vancomycin

Inpatient treatment

DOC for patients with puerperal breast abscess who are penicillin-allergic, as well as those with suspected MRSA infection. It is a potent antibiotic directed against gram­-positive organisms and active against enterococcal species. Useful in treatment of septicemia and skin structure infections. Indicated for patients who cannot receive or have failed to respond to penicillins and cephalosporins or who have infections with resistant staphylococci.

To avoid toxicity, current recommendation is to assay vancomycin trough levels after the third dose drawn 0.5 hour before next dosing. Use CrCl to adjust dose in renal impairment, prn.

Caution: Vancomycin can cross the placenta and into breast milk. Use caution in pregnant and breastfeeding mothers.

Dalbavancin (Dalvance)

Emerging treatment

Lipoglycopeptide antibiotic; interferes with cell wall synthesis by binding to D-alanyl-D-alanine terminus of the stem pentapeptide in nascent cell wall peptidoglycan, thus preventing cross­linking.

Bactericidal in vitro against S aureus and S pyogenes at concentrations observed in humans at recommended doses.

Caution: Pregnancy category C, the long half-­life of dalbavancin should be considered before using in pregnancy. Unknown if secreted in breast milk.

Oritavancin (Orbactiv)

Emerging treatment

Lipoglycopeptide antibiotic; interferes with bacteria cell wall synthesis by inhibiting transglycosidation and transpeptidation. Also disrupts the integrity of bacterial membranes, leading to cell death.

Exhibits concentration-dependent bactericidal activity against S aureus (including MRSA), Streptococcus species, and Enterococcus faecalis (not VRE).

Caution: Pregnancy category C. Unknown if distributed in human breast milk.

Tigecycline (Tygacil)

Inpatient treatment

If MRSA risk with beta-lactam allergy.

A glycylcycline antibiotic that is structurally similar to tetracycline antibiotics; inhibits bacterial protein translation by binding to 30S ribosomal subunit and blocks entry of amino­acyl tRNA molecules in ribosome A site.

Caution: Pregnancy Category D. Unknown, but suspected to be secreted in breast milk; do not use in pregnancy or if breastfeeding.

Linezolid (Zyvox)

Inpatient or outpatient treatment

If MRSA risk with beta-lactam allergy.

Binds to bacterial 23S rRNA of the 50S subunit to prevent protein translation; also elicits nonselective MAO inhibition.

Caution: Pregnancy category C; secreted in breast milk, use caution if used while breastfeeding.

Clindamycin (Cleocin)

Outpatient or inpatient therapy

Clindamycin is a semisynthetic antibiotic produced by 7(S)-chloro-substitution of the 7(R)-hydroxyl group of the parent compound, lincomycin. It inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Clindamycin is widely distributed in the body without penetrating the central nervous system (CNS). It is protein-bound and excreted by the liver and kidneys.

Daptomycin (Cubicin)

Inpatient treatment

If MRSA risk with beta-lactam allergy.

Cyclic lipopeptide: Binds to bacterial membranes and causes rapid depolarization of membrane potential; causes inhibition of protein, DNA, RNA synthesis, and bacterial cell death.

Pregnancy category B, successful use during second and third trimesters of pregnancy reported but limited information available. Secreted in breast milk in low concentrations, however, it is poorly bioavailable orally; use caution if breastfeeding.

Trimethoprim/sulfamethoxazole (Bactrim, Bactrim DS)

Outpatient therapy

For non-severe MRSA infections.

Trimethoprim: Inhibits dihydrofolate reductase, thereby blocking production of tetrahydrofolic acid from dihydrofolic acid.

Sulfamethoxazole: Inhibits bacterial synthesis of dihydrofolic acid by competing with para­aminobenzoic acid.

Caution: Pregnancy category D. Medication crosses into breast milk. Avoid use in breastfeeding mother if nursing preterm infants, infants <2 months, or children with known or suspected glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Doxycycline (Acticlate, Adoxa, Doryx, Morgidox, Vibramycin)

Outpatient or inpatient therapy

If beta-lactam hypersensitivity.

Doxycycline is a tetracycline. Inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria; may block dissociation of peptidyl t­RNA from ribosomes, causing RNA-­dependent protein synthesis to arrest.

Caution: Pregnancy Category D and secreted in breast milk; do not use in pregnancy or if breastfeeding.