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An oncocytoma is a tumor made up of oncocytes, a special kind of cells. [1] [2]
An oncocytoma is an epithelial tumor composed of oncocytes, large eosinophilic cells having small, round, benign-appearing nuclei with large nucleoli.
Renal oncocytoma is thought to arise from the intercalated cells of collecting ducts of the kidney. It represent 5% to 15% of surgically resected renal neoplasms. Ultrastructurally, the eosinophilic cells have numerous mitochondria. In gross appearance, the tumors are tan or mahogany brown, well circumscribed and contain a central scar. They may achieve a large size (up to 12 cm in diameter). Renal oncocytoma is considered benign, cured by nephrectomy. There are some familial cases in which these tumors are multicentric rather than solitary. [3]
The salivary gland oncocytoma is a well-circumscribed, benign neoplastic growth also called an oxyphilic adenoma. It comprises about 1% of all salivary gland tumors. The histopathology is marked by sheets of large swollen polyhedral epithelial oncocytes, which are granular acidophilic parotid cells with centrally located nuclei. The granules are created by the mitochondria.
Thyroid oncocytomas can be benign (adenomas) or malignant (carcinomas). Grossly, oncocytic adenomas are encapsulated, solid nodules with a characteristic brown cut surface. The gross appearance of a minimally invasive oncocytic carcinoma is indistinguishable to that of an adenoma, while widely invasive oncocytic carcinomas are obviously invasive macroscopically and display pervasive vascular invasion with multifocal involvement of the thyroid gland. There are no reliable cytologic features which distinguish oncocytic adenomas from carcinomas and the only criteria for a diagnosis of malignancy is the identification of transcapsular and/or vascular invasion.
Most cases of renal oncocytomas are asymptomatic, discovered incidentally (by chance) on a tomography or ultrasound of the abdomen. Following are some of the possible symptoms : Hematuria, flank pain, abdominal mass.
Salivary gland oncocytomas are most common in ages 70-80, females, the parotid gland (85-90%), and are firm, slowly growing, painless masses of < 4 cm. They may be bilateral. Patients with thyroid oncocytomas present with a thyroid nodule, usually with normal thyroid function. If the tumor is big or invasive, there may be other symptoms such as difficulty swallowing or talking. [tubepress mode=’tag’, tagValue=’Oncocytoma’]