General Information about Oncocytoma
- An oncocytoma is an epithelial tumor composed of oncocytes, large eosinophilic cells with small, round, benign-appearing nuclei and large nucleoli.
- Oncocytoma can arise in various organs.
- Renal oncocytoma is thought to originate from the intercalated cells of collecting ducts in the kidney.
- Salivary gland oncocytoma is a well-circumscribed, benign neoplastic growth also known as oxyphilic adenoma.
- Thyroid oncocytomas can be benign (adenomas) or malignant (carcinomas), also known as Hürtle cell tumors.
- Grossly, oncocytic adenomas are encapsulated, solid nodules with a characteristic brown cut surface.
- Minimally invasive oncocytic carcinomas appear indistinguishable from adenomas, while widely invasive oncocytic carcinomas display obvious macroscopic invasion and vascular involvement.
- Cytologic features alone cannot reliably distinguish oncocytic adenomas from carcinomas.
- The identification of transcapsular or vascular invasion is the only criterion for diagnosing malignancy.

Renal Oncocytoma
- Renal oncocytoma represents 5% to 15% of surgically resected renal neoplasms.

Salivary Gland Oncocytoma
- Salivary gland oncocytoma comprises about 1% of all salivary gland tumors.
- Histopathology of salivary gland oncocytoma is characterised by sheets of large swollen polyhedral epithelial oncocytes.
- These oncocytes are granular acidophilic parotid cells with centrally located nuclei.
- The granules are created by the mitochondria.
- Salivary gland oncocytomas are most common in individuals aged 70-80, particularly females.
- They primarily occur in the parotid gland (85-90% of cases).
- These masses are firm, slowly growing, and painless, typically measuring less than 4cm.
- Bilateral occurrence may also be observed in some cases.

Thyroid Oncocytoma
- Patients with thyroid oncocytomas typically present with a thyroid nodule, often with normal thyroid function.
- Larger or invasive tumors may cause difficulty swallowing or talking.

Additional Information
- Micrograph of a renal oncocytoma stained with H&E.
- Gross appearance of a nephrectomy specimen containing a renal oncocytoma, showing rounded contour, mahogany color, and a central scar.
- Kidney, renal cell carcinoma, and Hurthle cell are related terms.
- Citations are needed to support the statements in each group.