Seborrheic Keratosis 

  • Author: Arthur K Balin, MD, PhD, FACP; Chief Editor: Dirk M Elston, MD   more...
 
Updated: Jan 12, 2012
 

Background

Seborrheic keratoses are the most common benign tumor in older individuals. Seborrheic keratoses have a variety of clinical appearances, as seen in the images below, and they develop from the proliferation of epidermal cells. Although no specific etiologic factors have been identified, they occur more frequently in sunlight-exposed areas.

Sharply circumscribed elevated seborrheic keratoseSharply circumscribed elevated seborrheic keratoses. Closer view of multiple seborrheic keratoses in anCloser view of multiple seborrheic keratoses in an autosomally dominant mode of inheritance. Seborrheic keratosis showing lackluster surface anSeborrheic keratosis showing lackluster surface and appearance of being stuck on the skin surface.
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Pathophysiology

The etiology of the development of a seborrheic keratosis is not known. Seborrheic keratoses exhibit histologic evidence of proliferation. Increased cell replication has been demonstrated in seborrheic keratoses with bromodeoxyuridine incorporation studies and immunohistochemistry for proliferation-associated antigens. A moderate increase is observed in the rates of apoptosis in all varieties of seborrheic keratoses compared to normal skin.

Reticulated seborrheic keratoses are usually found on sun-exposed skin, and the reticulated type of seborrheic keratoses may develop from solar lentigines.

Epidermal growth factors or their receptors have been implicated in the development of seborrheic keratoses.[1, 2, 3] No difference was observed in the expression of immunoreactive growth hormone receptors in keratinocytes from normal epidermis and keratinocytes from seborrheic keratoses. The expression of BCL2, an apoptosis-suppressing oncogene, is low in seborrheic keratosis in contrast to the high values in basal cell and squamous cell carcinoma.[4] No increase is observed in the sonic hedgehog signal transducers patched (ptc) and smoothened (smo) messenger RNA (mRNA) in seborrheic keratosis over normal skin.[5]

A high frequency of mutations in the gene encoding the tyrosine kinase receptor FGFR3 (fibroblast growth factor receptor 3) has been found in certain types of seborrheic keratoses. This may the first clue into the genetic basis for the pathogenesis of seborrheic keratoses. FGFR3 belongs to a class of transmembrane tyrosine kinase receptors involved in signal transduction to regulate cell growth, differentiation, and migration, as well as wound healing and angiogenesis. Upon ligand binding, FGFR3 dimerizes, which, in turn, induces phosphorylation of the kinase domain. Activating mutations in FGFR3 have been found in approximately 40% of hyperkeratotic seborrheic keratoses, 40% of acanthotic seborrheic keratoses, and 85% of adenoid seborrheic keratoses.[6, 7, 8]

Seborrheic keratoses have a varying degree of pigmentation. In pigmented seborrheic keratoses, the proliferating keratinocytes trigger the activation of neighboring melanocytes by secreting melanocyte-stimulating cytokines. Endothelin-1 has dual stimulatory effects on DNA synthesis and melanization of human melanocytes and has been implicated as playing a part in the hyperpigmentation observed in seborrheic keratoses.[9] Immunohistochemically, the keratinocytes of seborrheic keratoses express low molecular weight keratin but often exhibit a partial lack of the high molecular weight forms of keratin.

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Epidemiology

Frequency

United States

Seborrheic keratoses are the most common benign tumor in older individuals. The frequency appears to increase with age. In 1963, Tindall and Smith examined a population of individuals older than 64 years in North Carolina and found that 88% of the people had at least one seborrheic keratosis.[10] In this study, 38% of the white women, 54% of the white men, and 61% of the black men and women were found to have 10 or more seborrheic keratoses. In 1965, Young examined 222 residents of the Orthodox Jewish Home for the Aged in New York and found that 29.3% of the men and 37.9% of the women had seborrheic keratosis.

International

In 2000, Memon et al found in a British population younger than 40 years that 8.3% of the males and 16.7% of the females had at least one seborrheic keratosis.[11] In an Australian population, 23.5% of individuals aged 15-30 years were found to have at least one seborrheic keratosis, with no significant differences between the sexes. In another Australian study of 100 people composed of hospital staff and nondermatologic day patients, 12% of people aged 15-25 years (n = 34), 79% of people aged 26-50 years (n = 24), 100% of people aged 51-75 years (n = 25), and 100% of people older than 75 years (n = 17) had seborrheic keratoses. The median number of seborrheic keratoses per person was 6 in the group aged 15-25 years, 5 in the group aged 26-50 years, 23 in the group aged 51-75 years, and 69 in those older than 75 years.

Mortality/Morbidity

Seborrheic keratoses are benign but secondary tumors, and Bowen disease (squamous cell carcinoma in situ) or malignant melanoma may occasionally arise within the lesion. Seborrheic keratoses can also catch on clothing and become irritated. They can itch, grow, and bleed.

  • Scratching seborrheic keratoses or trying to pick them off the skin can result in a secondary infection.
  • People sometimes have many seborrheic keratoses, and they may obscure the detection of a dysplastic nevus or malignant melanoma.

Race

Seborrheic keratoses are less common in populations with dark skin compared to those having white skin; however, black individuals develop a variant of seborrheic keratoses termed dermatosis papulosa nigra. These lesions affect the face, especially the upper cheeks and lateral orbital areas. They are small, pedunculated, and heavily pigmented with a minimal keratotic element. The onset of these lesions generally is earlier than that of ordinary seborrheic keratoses.

Sex

No sex difference is apparent in the frequency of occurrence of seborrheic keratoses.

Age

Seborrheic keratoses are the most common benign tumor in older individuals. They appear to increase with age. Seborrheic keratoses have also been found to occur in younger individuals.

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Contributor Information and Disclosures
Author

Arthur K Balin, MD, PhD, FACP  Clinical Professor, Lankanau Medical Research Center, Jefferson Health System

Arthur K Balin, MD, PhD, FACP is a member of the following medical societies: American Academy of Dermatology, American Chemical Society, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American College of Nutrition, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Geriatrics Society, American Medical Association, American Society for Clinical Nutrition, American Society for Dermatologic Surgery, American Society for Laser Medicine and Surgery, American Society of Dermatopathology, College of American Pathologists, Gerontological Society of America, International Academy of Pathology, International Society for Dermatologic Surgery, Pennsylvania Medical Society, Phi Beta Kappa, Royal Society of Medicine, Sigma Xi, and Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Specialty Editor Board

Evan R Farmer, MD  Clinical Professor of Pathology and Dermatology, Department of Pathology, Virginia Commonwealth University School of Medicine

Evan R Farmer, MD is a member of the following medical societies: American Academy of Dermatology, American Dermatological Association, American Medical Association, American Society of Dermatopathology, and International Society of Dermatology

Disclosure: Nothing to disclose.

David F Butler, MD  Professor of Dermatology, Texas A&M University College of Medicine; Chair, Department of Dermatology, Director, Dermatology Residency Training Program, Scott and White Clinic, Northside Clinic

David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Warren R Heymann, MD  Head, Division of Dermatology, Professor, Department of Internal Medicine, University of Medicine and Dentistry of New Jersey-New Jersey Medical School

Warren R Heymann, MD is a member of the following medical societies: American Academy of Dermatology, American Society of Dermatopathology, and Society for Investigative Dermatology

Disclosure: Nothing to disclose.

Catherine M Quirk, MD  Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania

Catherine M Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD  Director, Ackerman Academy of Dermatopathology, New York

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

With appreciation for the assistance of Michael Vilenchik, MD, PhD and Loretta Pratt, MD.

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Sharply circumscribed elevated seborrheic keratoses.
Closer view of multiple seborrheic keratoses in an autosomally dominant mode of inheritance.
Seborrheic keratoses projecting above the level of the epidermis. Cysts represent sections of hyperkeratotic follicles.
Seborrheic keratosis showing lackluster surface and appearance of being stuck on the skin surface.
This is an autosomal dominant form of multiple seborrheic keratoses. This man's daughter is developing a similar distribution and quantity of seborrheic keratoses.
The back of this same patient as in the image above with multiple seborrheic keratoses. His face had a similar number of seborrheic keratoses.
Acanthotic type of seborrheic keratosis.
Higher-power view of the cells in an acanthotic seborrheic keratosis.
Hyperkeratotic type of seborrheic keratosis.
Reticulated (or adenoid) type of seborrheic keratosis.
This is a reticulated (or adenoid) seborrheic keratosis with abundant pigment.
Seborrheic keratosis with inflammation in the dermis.
This seborrheic keratosis was a pedunculated lesion in an axillary fold. Clinically, it had some resemblance to a skin tag.
 
 
 
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