Cytopathology of oncocytic carcinoid tumor of the lung mimicking granular cell tumor - A case report

BACKGROUND: The cytopathologic features of oncocytic carcinoid tumor of the lung, a rare variant of carcinoid tumor that in composed exclusively of on cocytes, have not been described before in detail. CASE: The bronchial brush smears from an 80-year-old female with an enobron chial obstructive tumor showed single ann loose clusters qi tumor cells wit h abundant granular, eosinophilic cytoplasm. The differential diagnoses inc luded oncocytic car cinoid tumor, granular cell tumor, other oncocytic tumo rs of bronchial origin and metastatic oncocytic tumors. Immunocytochemistry and electron microscopy confirmed the diagnosis of oncocytic carcinoid tum or. CONCLUSION: Oncocytic carcinoid tumor of the lung has cytopathologic featur es similar to those of granular cell tumor and pulmonary oncocytoma. Immuno cytochemistry, electron microscope or both are necessary to distinguish the se neoplasms.