EXPRESSION OF BCL-2 ONCOPROTEIN IN BENIGN AND MALIGNANT SPINDLE-CELL TUMORS OF SOFT-TISSUE, SKIN, SEROSAL SURFACES, AND GASTROINTESTINAL-TRACT

An immunohistochemical study to determine the pattern of immunoreactiv ity for bcl-2 oncoprotein was performed in 380 spindle cell tumors of soft tissue, skin, serosal surfaces, and gastrointestinal tract. The c ases studied included examples of benign, reactive spindle cell prolif erations to benign and malignant spindle cell neoplasms, including nod ular fasciitis (10), fibromatosis (5), dermatofibroma (10), dermatofib rosarcoma protuberans (18), Kaposi's sarcoma (15), spindle cell lipoma tous tumors (24), benign and malignant smooth muscle tumors (35), neur al/peripheral nerve sheath neoplasms (53), synovial sarcomas (70) soli tary fibrous tumors of serosal surfaces and other sites (56), gastroin testinal stromal tumors (GIST) (47), and malignant undifferentiated fi broblastic spindle cell proliferations of soft tissue (37 cases). The results of bcl-2 staining was additionally correlated with CD34 immuno reactivity. Bcl-2 was uniformly negative in all cases of nodular fasci itis, fibromatosis, and dermatofibroma, as well as in benign and malig nant smooth muscle proliferations. Strong positivity for bcl-2 was obs erved in all cases of spindle cell lipoma, dendritic fibromyxolipoma, Kaposi's sarcoma, solitary fibrous tumors, gastrointestinal stromal tu mors, and in the spindle cell component of synovial sarcoma. With the exception of the last, there appeared to be a close correlation betwee n the expression of bcl-2 and CD34 in these tumors. Strong bcl-2 posit ivity also was found, at least focally, in approximately one third of benign and malignant peripheral nerve sheath tumors, particularly in t he better-differentiated (Antoni type A) areas. Sarcomas of fibroblast ic type, including low-grade myxofibrosarcoma, malignant fibrous histi ocytoma, and fibrosarcoma, showed variable expression of bcl-2 in the tumor cells. Our results appear to indicate that bcl-2 may have a wide distribution among benign and malignant spindle cell neoplasms. Stron g expression of this marker in some of these conditions, particularly solitary fibrous tumor, gastrointestinal stromal tumors, and synovial sarcoma, may be of aid for differential diagnosis.