Pulmonary Granular Cell Tumors: A Study of 4 Cases Including a Malignant Phenotype.

Abstract

Granular cell tumors are lesions of Schwannian phenotype that most frequently arise in the skin, breast, and tongue. Pulmonary granular cell tumors (pGCTs) are exceedingly rare and only a handful of cases worldwide have been reported as malignant. We report here a series of 4 pGCTs, including an extremely rare case of a malignant pGCT which underwent next-generation sequencing to identify a novel pathogenic mutation. We are the first to report any prognostic data and response to treatment. Consistent with granular cell tumors of other primary sites, the majority of pGCTs (75%) were deemed histologically and biological benign without metastasis or recurrence after resection (mean follow-up, 750 d). pGCTs occurred predominantly in women (75%) with a mean age of 57 years (range, 49 to 66 y) and variable smoking history. Notably, 2 women also developed an associated lung carcinoma (adenocarcinoma and small cell carcinoma). We also report here an exceedingly rare case of a 51-year-old nonsmoker woman diagnosed with a malignant pGCT. She presented with a 6.4×6.1×4.4 cm infrahilar left lower lobe mass with extrinsic compression and obstruction of the left mainstem on enhanced computed tomography. Pathology of the resection specimen confirmed a pGCT composed of sheets of tumor cells with pleural, pericardial, and diaphragmatic metastases. Molecular analysis by next-generation sequencing failed to yield any driver mutations common to primary lung adenocarcinomas. Only 2 previous malignant pGCTs have been reported; our case revealed a novel pathologic ATM mutation.