Introduction
Background
Parotid is a Greek word that means near the ear. Parotid glands are the largest of the salivary glands. They are paired glands that contain both mucus and serous cells and a ductal network.1
Pathophysiology
Most primary tumors of the parotid glands arise from 1 of 2 histologic cell subtypes: epithelial tumors arising from ductal cells and glandular tumors from salivary unit cells.
Parotid, malignant tumors. Axial T1-weighted MRI demonstrates a low-signal-intensity mass in the left parotid gland. Pathology indicated mucoepidermoid carcinoma.
Parotid, malignant tumors. Axial contrast-enhanced CT scan shows an infiltrative mass involving the left parotid gland. Pathology indicated a parotid carcinoma.
The most common metastases to the intraparotid lymph nodes are from melanoma and squamous cell carcinoma of the head and neck.
Frequency
United States
Malignant tumors of the parotid gland are rare. The incidence of salivary gland tumors is 1-2 cases per 100,000 people. Of these, 85% occur in the parotid gland, representing 0.6% of tumors in the body.
Only 20% of parotid neoplasms are malignant. The most common malignant parotid neoplasm in adults is mucoepidermoid carcinoma, which represents almost one third of all malignant tumors.
Mortality/Morbidity
Depending on the histologic type and tumor grade, the morbidity and mortality can vary greatly. Some benign tumors can be aggressive locally and recur following their removal. Morbidity is proportional to the degree of invasion at the time of detection.
- Some malignant tumors are slow growing with high 5-year survival rates in patients. Poor prognostic signs are the following: (1) high-grade tumor, (2) lymph node or distant metastasis at diagnosis, (3) facial nerve paralysis, (4) skin involvement, (5) high tumor stage, (6) deep lobe involvement, and (7) recurrent tumor.
- Pain does not indicate that a neoplasm is malignant; however, in patients with known malignancy, pain is a poor prognostic sign.
Race
Eskimos are at increased risk for undifferentiated lymphoepithelial carcinoma.
Sex
Overall, parotid tumors are slightly more common in women than in men.
Age
Most parotid tumors occur in patients aged 30-70 years. Parotid tumors are more likely to be malignant in children (approximately 35%) than in adults.
- The most common malignant parotid tumors in adults are the following: (1) mucoepidermoid carcinoma, (2) adenoid cystic carcinoma, and (3) malignant mixed tumor.
- The most common malignant parotid tumors in children are the following: (1) mucoepidermoid carcinoma, (2) acinic cell carcinoma, and (3) undifferentiated carcinoma.
Anatomy
The parotid gland is enveloped by the superficial layer of the deep cervical fascia. The gland is artificially divided into the superficial (80%) and deep (20%) lobes, which are separated by the facial nerve. The deeper portion of the gland lies between the anterior border of the sternocleidomastoid and the posterior belly of the digastric muscles. Most of the gland is located posterior and lateral to the ascending ramus and angle of the mandible. The Stensen duct drains the ductal system of the parotid and enters the oral cavity near the upper second molar tooth. Several lymph nodes normally are present within each gland.
Presentation
A typical parotid malignancy is a painless, unilateral enlargement of the gland. The purpose of radiologic examination is to define the size and anatomy of the mass, differentiate the intraglandular origin from extraglandular origin, determine its benign and malignant characteristics, and provide important preoperative information such as the location of the facial nerve.2
The workup begins with a history and physical examination. FNA of the mass may be performed. The accuracy of FNA for diagnosis depends strongly on the quality of the specimen and the experience of the cytopathologist. Bartels et al reported no increase in accuracy by adding FNA to cross-sectional imaging study.
Preferred Examination
CT and MRI are the modalities of choice for imaging parotid neoplasms. Both have sensitivities that approach 100%. Both modalities have the ability to depict the entire gland and concomitantly show the contralateral gland.3
Each modality has special benefits and limitations. MRI is the preferred modality for evaluating a painless parotid mass. CT is well suited for evaluating recurrent, tender parotid masses that can be inflammatory. Plain radiographs or CT demonstrate invasion the earliest. Nuclear medicine studies lack the resolution to show bony invasion. Most malignant tumors are cold on scintigraphy. Combining fine-needle aspiration (FNA) with MRI offers no greater accuracy compared with that of either test alone.4,5
Limitations of Techniques
On CT or MRI, many malignant tumors, such as acinic cell carcinomas or low-grade mucoepidermoid carcinomas, appear indistinguishable from benign tumors, such as pleomorphic adenomas.
Differential Diagnoses
Branchial Cleft Cysts
Cystic Hygroma
Liposarcoma, Soft Tissue
Parotid, Pleomorphic Adenoma
Schwannoma, Cranial Nerve
Other Problems to Be Considered
Malignant or premalignant parotid neoplasms
Carcinoma ex pleomorphic adenoma
Malignant mixed tumor
Mucoepidermoid carcinoma
Adenoid cystic carcinoma
Acinic cell carcinoma
Polymorphous low-grade adenocarcinoma
Salivary duct carcinoma
Basal cell adenocarcinoma
Adenocarcinoma, not otherwise specified
Clear cell carcinoma
Epithelial myoepithelial carcinoma
Sebaceous neoplasm of salivary gland origin
Primary squamous cell carcinoma
Metastasis
Lymphoma
Benign neoplasms
Warthin tumor or adenolymphoma
Oncocytoma
Oncocytic papillary cystadenoma
Myoepithelioma
Sialadenoma papilliferum
Inverted ductal papilloma
Lipoma
Schwannoma and neurofibroma
Hemangioma
Granulomatous diseases
Sarcoid
Tuberculosis
Cat scratch disease
Actinomycosis
Vascular and lymphatic malformations
Arteriovenous malformation
Hemangioma
Lymphangioma
Other considerations
Inflammatory disease
Parotid cysts
Sialadenosis
Hyperplasia or hypertrophy of salivary glands
Sjögren syndrome
Mikulicz disease or sicca syndrome
More on Parotid, Malignant Tumors |
 Overview: Parotid, Malignant Tumors |
| Imaging: Parotid, Malignant Tumors |
| Follow-up: Parotid, Malignant Tumors |
| Multimedia: Parotid, Malignant Tumors |
| References |
| Further Reading |
| Next Page » |
References
Jeannon JP, Calman F, Gleeson M, McGurk M, Morgan P, O'Connell M, et al. Management of advanced parotid cancer. A systematic review. Eur J Surg Oncol. Nov 20 2008;[Medline].
Jafari A, Royer B, Lefevre M, Corlieu P, Périé S, St Guily JL. Value of the cytological diagnosis in the treatment of parotid tumors. Otolaryngol Head Neck Surg. Mar 2009;140(3):381-5. [Medline].
Cheung RL, Russell AC, Freeman J. Does routine preoperative imaging of parotid tumours affect surgical management decision making?. J Otolaryngol Head Neck Surg. Jun 2008;37(3):430-4. [Medline].
Bartels S, Talbot JM, DiTomasso J, et al. The relative value of fine-needle aspiration and imaging in the preoperative evaluation of parotid masses. Head Neck. Dec 2000;22(8):781-6. [Medline].
Wong DS, Li GK. The role of fine-needle aspiration cytology in the management of parotid tumors: a critical clinical appraisal. Head Neck. Aug 2000;22(5):469-73. [Medline].
Yabuuchi H, Matsuo Y, Kamitani T, Setoguchi T, Okafuji T, Soeda H, et al. Parotid gland tumors: can addition of diffusion-weighted MR imaging to dynamic contrast-enhanced MR imaging improve diagnostic accuracy in characterization?. Radiology. Dec 2008;249(3):909-16. [Medline].
Gritzmann N. [Ultrasound of the salivary glands]. Laryngorhinootologie. Jan 2009;88(1):48-56; quiz 57-9. [Medline].
Cummings CW, Fredrickson JM, Harker LA. Salivary glands. In: Otolaryngology: Head and Neck Surgery. Vol 2. Mosby-Year Book;1993:1029-78.
Kamal SA, Othman EO. Diagnosis and treatment of parotid tumours. J Laryngol Otol. Apr 1997;111(4):316-21. [Medline].
Shinohara S, Yamamoto E, Tanabe M. [Evaluation of RI scintiscanning to parotid gland tumors]. Nippon Jibiinkoka Gakkai Kaiho. Sep 2001;104(9):852-8. [Medline].
Soler R, Bargiela A, Requejo I, et al. Pictorial review: MR imaging of parotid tumours. Clin Radiol. Apr 1997;52(4):269-75. [Medline].
Som PM, Curtin HD. Salivary glands. In: Head and Neck Imaging. 3rd ed. St Louis: Mosby-Year Book;. 1996: 823-914.
Further Reading
Related eMedicine topics
Parotid Tumors, Malignant
Parotid, Pleomorphic Adenoma
Salivary Gland Neoplasms
Salivary Glands, Fine-Needle Aspiration
Parotid Tumors, Benign
Clinical trials
Amifostine With IMRT for Submandibular and Sublingual Salivary Sparing During Head and Neck Cancer Treatment
Diagnostic Accuracy of Fine Needle Aspiration in Parotid Tumors
Keywords
parotid tumor, parotid gland tumors, parotid cancer, parotid gland cancer, salivary glands, salivary gland tumors, salivary gland cancer, salivary gland cancer, malignant parotid neoplasm, salivary gland neoplasm, salivary neoplasm, mucoepidermoid carcinoma, adenoid cystic carcinoma, malignant mixed tumor, acinic cell carcinoma, undifferentiated carcinoma, parotid malignancy, parotid neoplasms
