Malignant mixed Müllerian tumors of the uterus. An immunohistochemical study.

Abstract

Malignant mixed müllerian tumors (MMMT) of the uterus have been subdivided into two types: those with heterologous sarcomatous elements (e.g., rhabdomyosarcoma, and chondrosarcoma) and those with only homologous elements (e.g., stromal sarcoma). The distinction, which may have prognostic significance, was based on the identification by light microscopy of cells that exhibited definite cross-striations, cartilage, or osteoid production. We studied 32 cases of uterine MMMT to assess the value of immunohistochemical markers in delineating the sarcomatous and epithelial components. Of 32 cases, 11 showed heterologous sarcoma (6, rhabdomyosarcoma, and 5, chondrosarcoma), and the remaining 21 were homologous MMMT. Six antigens--desmin, myoglobin, S-100, alpha 1-antichymotrypsin (ACT), epithelial membrane antigen (EMA), and monoclonal cytokeratin (AE1 and AE3), (to test for possible myogenic, chondroid, fibrohistiocytic, and carcinomatous differentiation)--were analyzed by the avidin-biotin-peroxidase method. EMA was found in neoplastic cells in all cases; 31 of 32 cases showed keratin. Desmin reactivity was detected in 14 of 32 cases, whereas myoglobin was present in 10 of 32. Three cases exhibited S-100 positivity (two in areas of chondrosarcoma, and one in some stromal sarcoma cells). Twenty-two cases (69%) exhibited ACT reactivity. Several cases displayed a malignant fibrous histiocytoma pattern. These demonstrated ACT positivity in both the neoplastic spindle and giant cells. We conclude that immunohistochemical staining for the above mentioned antigens is a useful diagnostic aid in delineating the sarcomatous and carcinomatous elements in MMMT.