A Rare Case of a Pulmonary Granular Cell Tumor presenting as a Coin Lesion

A 38-year-old man was found to show a well-defined oval-shaped homogeneous dense mass (20 × 30 mm) in the left upper lung field on chest X-ray. Left upper divisionectomy was performed under video-assisted thoracic surgery. Histology showed that the tumor cells had abundant eosinophilic granular cytoplasm, and were immunopositive for neuron-specific enolase, CD56, S-100 protein, and chromogranin. The proportion of Ki-67 positive cells was < 1%. An electron-microscopic examination showed many membrane-bound whorls in the cytoplasm. Although this was a very rare case presenting as an asymptomatic coin lesion, the histological features were the same as those demonstrated for granular cell tumor at common sites.