A Novel Case of Pulmonary Sclerosing Diffuse PEComatosis With Neuroendocrine Cell Hyperplasia.

Proliferations of neoplastic perivascular epithelioid cells (PECs) may occur within the lung and extrathoracic sites. The term "PEComatosis" is applied to multiple or diffuse microscopic proliferations of neoplastic PECs. Pulmonary diffuse PEComatosis is extremely rare, with only one case documented in the literature to date. We herein report a novel sclerosing variant of diffuse PEComatosis in a 68-year-old woman with clinical tuberous sclerosis complex (TSC), who underwent lung resection for evaluation of persistent, bilateral ground glass opacities. The patient had no respiratory complaints or ventilatory defects in pulmonary function tests. The morphologic features resembled the previous description of pulmonary diffuse PEComatosis, showing interstitial nodular and diffuse proliferation of predominantly clear epithelioid cells with PEC differentiation by immunohistochemistry. The PEComatous proliferation was accompanied by a pattern of sclerosis that overlapped with the sclerosing variant of PEComa. There was no evidence of lymphangioleiomyomatosis. The changes were complicated by neuroendocrine cell hyperplasia, which has not previously been reported in the lungs of patients with TSC.