[Heterologous Müllerian adenosarcoma of the uterus--a rare tumor. Light- and electron-microscopic findings, biological behavior (author's transl)].

A case of heterologous Müllerian adenosarcoma of the uterus is presented with emphasis on morphologic differentiation, clinical course, prognosis, and treatment. This tumor was described first by Clement and Scully in 1974. Since that time 36 cases have been reported in the literature. The neoplasm consists of benign epithelial and malignant mesenchymal elements. The latter are composed of tissue with homologous and heterologous differentiation. Our microscopic and ultrastructural studies suggested that the heterologous elements were rhabdomyoblasts with a variable degree of differentiation. According to the literature the prognosis of Müllerian adenosarcoma is better than that of malignant mixed Müllerian tumor. The location of the tumor - whether intrauterine or extrauterine - seems to be more important as regards prognosis than the differentiation of the sarcomatous elements. The clinical course in our patients was not different from those described in the literature. Surgical removal of the tumor remains the treatment of choice. Some authors report a better survival rate when surgical treatment is followed by radiotherapy. Chemotherapy may be useful in cases of local or distant metastasis, and in cases of incomplete excision of the tumor mass.