An oncocytoma is a tumor consisting of epithelial cells called oncocytes. This abnormal growth is usually associated with the kidneys and salivary glands. However, it can occur anywhere in the body. The tumor is also referred to as oncocytic adenoma or oxyphilic adenoma.
The oncocytoma occurs in the epithelium, which is the tissue that covers the surface of organs and several parts of the body. Also, it is often described as a benign tumor, which means that it will not develop into cancer and is thus harmless. This status places it under the category of adenoma, which is a collection of benign epithelial tumors. This categorization explains the alternate term of oncocytic adenoma. The oxyphilic adenoma term arises from the oncocytes being eosinophilic, or "acid-loving" cells.
The most common form of oncocytoma is renal oncocytoma. Medical researchers theorize that the tumor originates from intercalated cells, which are epithelial cells that can be found in the kidneys' collecting duct system. Since this condition is asymptomatic, showing little or no symptoms of disease or illness, it is typically discovered unintentionally by a CT scan or ultrasound technology. When symptoms do occur, they include releasing blood in urine, or hematuria; pain in the sides; and bloated abdomen.
Another common form of oncocytoma is salivary gland oncocytoma; this makes up a very tiny percentage of all tumors. It commonly appears in the parotid gland, which is the largest of the body's salivary glands. The masses are described as firm and painless, with a size no larger than approximately 1.6 inches (4 cm). Women in their 70s and 80s are more likely than any other group of people to get this tumor. Like the abnormal growths in the kidneys, salivary gland oncocytoma is asymptomatic, although with thyroid oncocytoma in particular, the patient may have difficulty talking or swallowing if the tumor becomes larger.
Although the oncocytoma is thought to be benign, the oncocytes themselves have the capability of being malignant, consequently developing into cancer. In this case, the adenoma turns into carcinoma, which is the malignant form of an epithelial tumor. For instance, renal oncocytoma can develop into renal cell carcinoma, which is the most common form of adult kidney cancer. Also known as hypernephroma, it is considered one of the deadliest cancers to contract, since it is asymptomatic in its early stages and is resistant to chemotherapy and radiation therapy. The tumors in the thyroid gland can also be malignant, and it is often hard to distinguish a carcinoma from an adenoma.