Oncocytoma is a type of usually benign tumor that originates in the cells of the kidneys, thyroid gland, salivary gland, or other organs. There are several synonyms for the term oncocytoma, including oncocytic adenoma, eosinophilic adenoma, Hurthle cell adenoma, oxyphilic adenoma, and oncocyte adenoma. These synonyms are used interchangeably to refer to the same type of tumor characterized by the presence of oncocytes, a type of glandular cell with abundant cytoplasm and mitochondria. While oncocytomas are usually benign, they can occasionally be malignant, and patients with these tumors should undergo close monitoring. Treatment options typically involve surgical removal of the affected tissue.