Rare Nerve Lesions of Non–Nerve Sheath Origin: A 17-Year Retrospective Series

Abstract

Abstract Context.—Peripheral nerve masses are frequently encountered in surgical pathology practice. However, once a peripheral nerve mass is determined not to be a nerve sheath neoplasm, differential diagnostic considerations drop off sharply. Objective.—To review our experience with surgically resected nerve masses. Design.—Retrospective search of pathology database. Rare neoplasms were studied by cytogenetic analysis or gene microarray. Results.—Four hundred fifty-eight cases were identified. After elimination of common lesions (mostly nerve sheath tumors), 37 cases (8%) remained, almost all of which were of non–nerve sheath origin: for example, hemangioma, metastatic neuroendocrine pancreatic carcinoma, meningiomas invading nerve fascicles, and primary extrarenal rhabdoid tumor and Ewing sarcoma of nerve. The latter showed rearrangement of the EWSR1 locus (22q12). The gene expression pattern of an undifferentiated sarcoma, presenting as ropelike nerve enlargement, clustered with malignant peripheral nerve sheath neoplasms but not other sarcomas or neuroepithelial tumors. Conclusions.—Diverse benign and malignant conditions can affect peripheral nerve.