OVEREXPRESSION OF THE C-MYC PROTOONCOGENE OCCURS FREQUENTLY IN UTERINE SARCOMAS

Overexpression of the c-myc proto-oncogene occurs in carcinoma of the ovary, endometrium, and cervix, and is associated with an adverse prog nosis, but little is known about the pattern of c-myc expression in ut erine sarcomas. This study investigates the expression of c-myc in ute rine smooth muscle tumors and malignant mixed mullerian tumors. Twenty -three leiomyosarcomas, 10 leiomyomas, and 9 malignant mixed mullerian tumors were examined for c-myc overexpression by immunohistochemistry .Differences in mitotic rate and in survival were compared in c-myc po sitive and negative cases of leiomyosarcoma. Overexpression of c-myc w as seen in 6/12 leiomyomas, 11/23 leiomyosarcomas, and 9/9 malignant m ixed mullerian tumors. Positive staining was restricted to a perinucle ar location in all of the leiomyomas and one leiomyosarcoma. Diffuse c ytoplasmic staining was seen in the remaining 10 positive leiomyosarco mas. Positive staining was seen in both epithelial and stromal element s of malignant mixed mullerian tumors, including homologous and hetero logous areas of stromal differentiation. There was no significant diff erence in mitotic rate or in survival between c-myc positive and negat ive cases of leiomyosarcoma. Overexpression of c-myc occurs in many ut erine leiomyosarcomas and the majority of malignant mixed mullerian tu mors. Overexpression of c-myc also occurs in benign uterine smooth mus cle tumors but with a different pattern than that seen in malignant tu mors. This overexpression does not correlate with survival and the sig nificance of overexpression of c-myc in these tumors is unclear.