SOFT-TISSUE PERINEURIOMA - EVIDENCE FOR AN ABNORMALITY OF CHROMOSOME-22, CRITERIA FOR DIAGNOSIS, AND REVIEW OF THE LITERATURE

Reported herein are two examples of soft-tissue perineurioma (STP), on e arising in the maxillary sinus and the other in subcutaneous tissue of the thigh. Electron microscopy and immunohistochemistry were perfor med in both cases. Based on our findings and a critical review of the literature, STPs are generally small, well-circumscribed but not encap sulated tumors. Histologically, most STPs resemble fibroblastic tumors , being composed of elongated, wavy cells. The immunohistochemical rea ctivity for epithelial membrane antigen, the lack of reactivity for S- 100 protein, and the presence of ultrastructural features of perineuri al cells are typical of this tumor. To explore the possibility that ST P, like the intraneural variety of perineurioma, exhibits an abnormali ty of chromosome 22, we performed fluorescence in situ hybridization w ith a probe specific for the M-bcr locus, which maps to the chromosome band 22q11. In both our tumors, a high percentage of nuclei having on ly one M-bcr signal (44 and 96%) was observed. Our findings indicated deletion of part or all of chromosome 22 and support the view that bot h soft-tissue and intraneural perineurioma are part of a spectrum of p erineurial neoplasia.