[A caruncular oxyphilic adenoma with an appearance of apocrine type secretion]

The histopathological and cytological findings of a caruncular oxyphilic adenoma (oncocytoma) in a 85 year-old male is described. The columnar or polygonal tumor cells contained numerous eosinophilic fine granules (mitochondria). They showed papillary proliferation and cyst formation. Electron microscopically, some tumor cells contained amorphous cytoplasm and small numbers of mitochondria in their apical snout, and secreted the contents in the extracellular spaces. It seemed that the tumor cells originated from the ductal epithelia in the caruncle and microscopically some cells simulated apocrine type secretion.