[Pulmonary granular cell tumors: a clinicopathological analysis of five cases]

Objective: To investigate the clinicopathological features of pulmonary granular cell tumors (pGCTs) and to improve the diagnostic accuracy of the tumor. Methods: A total of 5 pGCTs were diagnosed from February 2016 to January 2022 at Shanghai Pulmonary Hospital, Tongji University School of Medicine and Fudan University Shanghai Cancer Center, China. Immunohistochemical staining, and analysis of the clinicopathological characteristics were performed. Results: The average age of the pGCTs patients was 46 years (ranging from 24 to 54 years), with 3 females and 2 males. One case occurred in the bronchus with multiple nodules in the lung, 2 cases occurred in the bronchial opening, and 2 cases were solitary nodules in the lung. The maximum diameter of the tumors ranged from 12 to 15 mm (mean size 14 mm). Microscopically, the tumor showed infiltrative growth and consisted of round, oval or polygonal cells. Abundant eosinophilic cytoplasm was noted, and the nucleoli were prominent. None of the 5 cases showed any mitosis or necrosis. Immunohistochemical and histochemical study showed positive staining for S-100 (5/5), SOX10 (5/5), Vimentin (5/5), TFE3 (4/5), PAS (3/5), and amylase-digested-PAS (3/5), while 4 cases were negative for CD68. TFE3 FISH analyses on 2 cases showed that no signal abnormality was detected in these 2 cases. The average proliferation index of Ki-67 was 2.2% (range 0-5%). There was no recurrence in 4 cases of pGCTs with a follow-up time ranging from 2 months to 60 months. Conclusions: pGCTs are very rare tumors, most likely originating from Schwann cells. Immunohistochemical staining is the conventional diagnostic tool for pGCTs diagnosis. Recognition of this entity is essential for pathologists to avoid misdiagnosis and unnecessary treatments.