is a tumor
made up of oncocyte
s, epithelial cells
characterized by an excessive amount of mitochondria, resulting in an abundant acidophilic, granular cytoplasm. The cells and the tumor that they compose are often benign
but sometimes may be premalignant
An oncocytoma is an epithelial
tumor composed of oncocytes, large eosinophil
ic cells having small, round, benign-appearing nuclei
with large nucleoli
Oncocytoma can arise in a number of organs.
Salivary gland oncocytoma
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.
Salivary gland oncocytomas are most common in ages 70–80, females, the parotid gland
(85–90%), and are firm, slowly growing, painless masses of less than 4 cm. They may be bilateral.
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 criterion for a diagnosis of malignancy is the identification of transcapsular or vascular invasion.
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.
Image:Renal oncocytoma3.jpg| Micrograph
of a renal oncocytoma
. H&E stain
Image:Renal oncocytoma4.jpg|Micrograph of a renal oncocytoma. H&E stain.