CD44 IMMUNOREACTIVITY IN SOFT-TISSUE SARCOMAS

The CD44 antigen is commonly expressed by a wide variety of human lymp hoid and epithelial cell types and tumors. Because one ligand of this receptor moiety appears to be stromal hyaluronic acid, we hypothesized that CD44 immunoreactivity might characterize selected mesenchymal ne oplasms as well. Sections from 112 soft-tissue sarcomas (32 malignant fibrous histiocytomas, 26 leiomyosarcomas, 15 malignant peripheral ner ve sheath tumors, 14 liposarcomas, eight synovial sarcomas, four epith elioid sarcomas, three clear-cell sarcomas, six angiosarcomas, and fou r alveolar soft-part sarcomas) were stained with the CD44 antibody A1G 3. Membrane accentuation and exclusive cytoplasmic reactivity were rec orded as separate staining patterns. All angiosarcomas, epithelioid sa rcomas, and alveolar soft-part sarcomas were positive: of these, all b ut two exhibited cytoplasmic staining. Cytoplasmic positivity was also found in the epithelial elements of four synovial sarcomas, whereas t he spindle cells were negative. Lipoblastic and melanocytic neoplasms were also negative for CD44. Membrane accentuation was observed in nin e of 20 CD44-reactive leiomyosarcomas, whereas 10 of 11 positive nerve -sheath neoplasms manifested cytoplasmic staining, suggesting differen ces in cellular-stromal interactions in these types of sarcomas. Varia ble patterns of reactivity in ''malignant fibrous histiocytomas'' appe ar to support an inherent heterogeneity in this class of tumors. Overa ll, these data indicate a wide distribution of CD44-antigen expression among soft-tissue tumors with some distinctive patterns of expression that may be useful in characterizing such neoplasms. However, CD44 st aining may have only a limited role in resolving the differential diag noses of epithelioid neoplasms.