ONCOCYTIC NODULAR HIDRADENOMA

Oncocytic neoplasms are most commonly of salivary, thyroid, parathyroi d, and renal origin. Ocular adnexal tumors with oncocytosis have been reported. We report an unusual example of a skin adnexal tumor from th e back. A tumor of uncertain duration was excised from a 54-year-old m an. Light microscopy of hematoxylin and eosin-stained sections showed a large, fairly well-defined cystic nodular hidradenoma with areas inf iltrated by numerous closely arranged, large, uniform, oval and polygo nal cells with abundant intensely eosinophilic cytoplasm and small cen tral, dark, round nuclei. No significant cellular atypia or mitotic fi gures were observed. The cytoplasm of these cells showed markedly posi tive immunostaining with monoclonal antimitochondrial antibodies, Elec tron microscopy demonstrated cytoplasm packed with mitochondria. Pure oncocytic tumors usually follow a benign clinical course. The focal pr esence of oncocytes in an otherwise histologically recognizable tumor apparently does not affect the prognosis, which in this case is the fa vorable outcome expected for a nodular hidradenoma.