Oncocytoma of the lung.

This report describes the clinical, anatomical, histologic and ultrastructural features of a bronchial oncocytoma. Histologically the oncocytes have granular eosinophilic cytoplasm. Ultrastructurally this corresponds to mitochondrial hyperplasia. Because cytoplasmic eosinophilia may be due to an abundance of cytoplasmic organelles other than mitochondria, it is emphasized that electron-microscopic study is an essential component in the diagnosis of oncocytomas.