Functioning adrenocortical oncocytoma: the first documented case producing interleukin-6 and review of the literature

Adrenocortical oncocytoma is an extremely rare and predominantly non-functioning tumor. We herein report the first case of an adrenocortical oncocytoma that produces interleukin (IL)-6. A 38-yr-old woman was referred for treatment of a 4-cm adrenal mass. Laboratory test results showed elevated inflammatory parameters. Intriguingly, IL-6 serum level was also high at 30 pg/ml (normal 0-4 pg/ml). The patient underwent laparoscopic right adrenalectomy. Microscopic examination showed that the tumor was an adrenocortical oncocytoma with a unique peripheral lymphoid cuff with germinal centers. Electron microscopy demonstrated that the cytoplasm of the neoplastic cells was packed with numerous abnormal mitochondria. Three observations lead us to consider that this tumor was the primary source of serum IL-6. First, the IL-6 level in blood collected from the right adrenal vein was highest (527 pg/ml) among intra-operative blood samples. Second, neoplastic cells stained positively for IL-6. Third, the serum IL-6 returned to normal levels immediately after surgery.