Primary pulmonary tumours of nerve sheath origin.

Primary intrapulmonary tumours of nerve sheath origin are extremely rare. We describe the clinicopathological features of four such peripheral nerve sheath tumours, two benign and two malignant. Of the benign tumours, one was a typical schwannoma and the other an ancient or degenerated schwannoma. The typical schwannoma was endobronchial in origin, diagnosis being established by small bronchoscopic biopsy. The histological diagnosis of malignant peripheral nerve sheath tumour required immunohistochemical and/or ultrastructural evidence of nerve sheath differentiation. One malignant tumour arose in a patient with Von-Recklinhausen's disease. Both malignant tumours behaved aggressively with the development of multiple intrapulmonary metastases, despite the markedly different histological appearance of the two tumours. Flow cytometric analysis of nuclear DNA content was performed on the four tumours, all of which showed a diploid DNA profile.