Intrathoracic peripheral nerve sheath tumors - A clinicopathological study of 75 cases

Although peripheral nerve sheath tumors (PNSTs) are common in the posterior mediastinum, they are rare in other mediastinal compartments and in the pleuropulmonary parenchyma. We sought to characterize the clinicopathological features of PNSTs occurring in the lung, pleura, and mediastinum. Diagnoses were confirmed by slide review. Study cases include 21 benign pleuropulmonary PNSTs, 49 benign mediastinal PNSTs, and 5 malignant PNSTs. Benign pleuropulmonary tumors comprised 13 schwannomas, 6 neurofibromas, 1 perineurioma, and 1 ganglioneuroma. Six lesions were endobronchial (3 neurofibromas, 1 schwannoma, 1 perineurioma, 1 ganglioneuroma), whereas the remaining schwannomas and neurofibromas formed parenchymal masses (usually pleural based). Benign mediastinal PNSTs (46 posterior, 2 middle, and 1 anterior) were all schwannomas and showed a female predominance. None of the patients with benign PNSTs experienced recurrence. Of the 5 malignant PNSTs, 4 were pleuropulmonary (3 pleural based) and 1 occurred in the anterior mediastinum. Two of the 5 patients had a history of neurofibromatosis type 1 (aged 27 and 45 years). At last follow-up, 3 of the 5 patients had died of disease, 1 was alive with disease, and 1 was alive with no evidence of disease (41 months). Although rare, a wide histologic range of PNSTs occur in the lung. Although neurofibroma, perineurioma, and ganglioneuroma were observed as endobronchial lesions, most pulmonary schwannomas were pleural-based masses. Mediastinal PNSTs are dominated by posterior mediastinal schwannomas, although schwannomas rarely occur in the other mediastinal compartments as well. Malignant PNSTs are very rare in the thorax, where they show aggressive behavior.