Mucin-producing renal oncocytoma. An undescribed variant of oncocytoma.

We report here one case of renal oncocytoma producing focal extracellular mucinous secretion in a 47-year-old woman. To the best of our knowledge, the presence of mucinous secretion in this tumor has not yet been reported. Mucin production, despite its low frequency, can be considered an additional feature of renal oncocytoma. Therefore, oncocytoma should be added to the list of parenchymal renal tumors that can show significant mucin secretion, and it should be included in the inventory of morphologic variations of oncocytoma which may cause diagnostic difficulties.