Granular cell tumors of the lung. Clinicopathologic study of 20 cases.

Granular cell tumor (GCT) of the lung is a rare neoplasm comprising 6-10% of all GCT. Since it was first described in the bronchus by Kramer in 1939, less than 80 cases have been reported. We present the clinicopathologic features of 23 GCT from 20 patients. The patients ranged in age from 20 to 57 years (median, 45 years) and included 10 males and 10 females. Of the 19 patients with available histories, nine (47%) were incidental findigns and 10 (53%) had obstructive symptoms [pneumonia, 7 (37%); atelectasis, 3 (16%)]. Three (16%) had hemoptysis, and one (5%) had weight loss. The GCT were solitary in 15 patients (75%) and multiple in five others (25%). One patient had three endobronchial lesions, and another had one endobronchial and one peripheral pulmonary lesion. Three of the patients had multiple cutaneous GCT (15%). Grossly, they were polypoid or nodular, tan-yellow, and firm. Histologically, the endobronchial GCT consisted of submucosal infiltrates of round to oval cells with abundant granular cytoplasm. The tumor often infiltrated into peribronchial tissue and in one case focally infiltrated an adjacent lymph node. Hyalinized thickening of the subepithelial basement membrane was common; the overlying epithelium often showed squamous metaplasia or ulceration. In those patients with available follow-up, the clinical behavior of lung GCT was benign. Our experience supports a conservative approach to therapy in most cases unless there has been extensive postobstructive lung injury. Potential conservative therapeutic approaches include bronchoscopic extirpation, laser therapy, or sleeve resection. The histogenesis of GCT is not known, although most studies suggest a peripheral nerve sheath origin. Our immunohistochemical results with positive staining for antibodies to S100 (4/4), NSE (3/3), vimentin (4/4), and actin (4/4, focal) are consistent with this concept.