Oncocytic carcinoid of the lung.

The case of a 47-year-old man with an oncocytic variant of carcinoid of the lung is reported. Chest radiography disclosed a well-defined round mass in the left upper lobe of the lung. Contrast-enhanced CT demonstrated a homogeneously well-enhanced mass. The oncocytic variant of a typical carcinoid is a rare histological entity, which can be established only by the ultrastructural features of mitochondrial hyperplasia and membrane-bound electron dense granules. Therefore, the definite diagnosis of oncocytic carcinoid tumor necessitates ultrastructural observation.