CHAIN-SPECIFIC KERATIN PROFILE OF EPITHELIOID SOFT-TISSUE SARCOMAS - AN IMMUNOHISTOCHEMICAL STUDY ON SYNOVIAL SARCOMA AND EPITHELIOID SARCOMA

Although recognized as distinct clinical entities, the putative histog enetic relationship of synovial sarcoma and epithelioid sarcoma remain s unclear. We studied the expression of keratin (CK) subtypes of 26 bi phasic and 12 monophasic spindle-cell synovial sarcomas, and 12 epithe lioid sarcomas with a panel of chain-specific monoclonal CK antibodies and compared them with other epithelioid bone and soft-tissue tumors. The epithelial part of biphasic synovial sarcoma showed abundant immu noreactivity for glandular type CKs 7, 8, 18, and 19, and for basal-ce ll-type CK14 (81% of cases). Squamous (nonkeratinized) type CK13 was l ess common (41%), and there was sparse staining for squamous (keratini zed) type CK10. Monophasic synovial sarcoma displayed scattered presen ce of CKs 8/18 in all, and CKs 7, 14, and 19 in a majority of cases. E pithelioid sarcoma exhibited CKs 8/18 in all, and CKs 14 and 19 in abo ut half of the cases, but lacked immunoreactivity for CK7. Chordoma, s tained for comparison, displayed massive staining for CKs 7, 8, 18, an d 19. Compared with monophasic synovial sarcoma, the epithelial compon ent of biphasic synovial sarcoma shows a diversity of chain-specific C K immunoreactivity, the most variable of all epithelioid neoplasms ari sing in nonepithelial tissues. The CK profile of epithelioid sarcoma r eveals more limitation, which underscores its clinicopathological dist inctness, The absence of CK7 in epithelioid sarcoma may be of use in t he differential diagnosis with metastatic adenocarcinoma and synovial sarcoma, especially when the epithelial component of the latter is dom inating and gland formation is absent.