Atypical bronchial carcinoid with oncocytoid features. Its ultrastructure, with special reference to its granular content.

: A case of atypical bronchial carcinoid with oncocytoid features was studied. The tumor contained mitochondria-laden cells with scanty neurosecretory granules, heavily granulated cells, and intermediate forms. The neurosecretory granules were of three types as reported in previous cases: type P, type 3, and a double-core granule. The ultrastructural findings are characteristic of this type of tumor.