Sarma DP, Santos EE (2009). Oncocytoma of the parotid gland. Ear,Nose,and Throat J 88(5):914. PMID: 19444786 [Pubmed- indexed for MEDLINE].
Oncocytoma of the parotid gland.
Sarma DP, Santos EE.
Ear Nose Throat J. 2009 May;88(5):914. PMID:19444786
[PubMed – indexed for MEDLINE]
Oncocytoma of the parotid gland
by Deba P. Sarma, MD and Eric E. Santos, MD
Oncocytoma is a rare benign tumor that accounts for approximately 1% of all salivary gland neoplasms. Almost 90% of oncocytic salivary gland tumors arise in the parotid gland, and the rest occur in the submandibular gland; tumors of the minor salivary glands are very rare. Most affected patients are older than 50 years, and the peak incidence occurs in the seventh through ninth decades of life. There is no predilection for either sex with the exception of clear-cell-dominant oncocytomas, for which there is a female preponderance. A history of radiation exposure to the head and neck has been documented in some patients with oncocytic tumors.
Patients usually present with a painless, nontender, slowly growing swelling of the affected gland. In rare cases, tumors are bilateral. Most tumors are well circumscribed or encapsulated, tan or brown, 3- to 4-cm solid masses within the salivary gland tissue. In rare cases, some cystic areas and/or additional tumor nodules may be seen within the adjacent salivary gland tissue.
Microscopically, the tumor is composed of solid and trabecular sheets of oncocytes arranged in an organoid pattern (figure). The oncocytes are large polygonal cells with distinct cell borders, abundant eosinophilic granular cytoplasm, and distinct nuclei with prominent nucleoli. Mitoses are rarely seen. Ultrastructurally, the cytoplasm of the oncocytes is filled with abundant mitochondria of various sizes, which accounts for the light microscopic finding of eosinophilic granules in the cytoplasm. A diagnosis of oncocytoma is easily made on light microscopy, and an electron microscopic study is rarely necessary. In the clear-cell variant of oncocytoma, the typical eosinophilic granular cytoplasm of the oncocytes is replaced by clear cytoplasm as a result of glycogen accumulation.
Figure. A: Low magnification shows a well-demarcated nodule of oncocytes adjacent to some normal lobules of parotid gland. B:Higher magnification shows organoid clusters of oncocytes with various sized lumens.
Surgical resection is the treatment of choice for most cases of oncocytoma. Recurrences are rare except in cases of (1) incomplete excision, (2) multifocal or bilateral tumors, and (3) the clear-cell variant.
Oncocytic carcinoma, which is the malignant counterpart of oncocytoma, is extremely rare. Microscopically, this tumor features pleomorphic oncocytes with increased mitosis, focal necrosis, perivascular and perineural invasion, and an infiltrative growth pattern. This is a high-grade tumor that is associated with a poor prognosis because of recurrences and distant metastases.
From the Department of Pathology, Creighton University Medical Center, Omaha, Neb.
Ellis GL, Auclair PL. Atlas of Tumor Pathology. Tumors of the Salivary Glands. 3rd series, fascicle 17. Washington D.C.:Armed Forces Institute of Pathology; 1996:103-14.
Gnepp DR, ed. Diagnostic Surgical Pathology of the Head and Neck. Philadelphia:W.B. Saunders; 2001:266-7.
Ear Nose Throat J. 2009 May;88(5):914