Low-grade metaplastic adenocarcinoma (carcinosarcoma) of the uterus: report of an unusual case.

An unusual low-grade metaplastic carcinoma (müllerian carcinosarcoma) of the uterine corpus occurring in a 45-year-old woman is presented. The tumor was polypoid and showed an initial invasion into the myometrium. The epithelial component was composed of low-grade endometrioid glands that focally showed an unusual oxyphilic change of the cytoplasm. These cells contained only a small amount of mitochondria detected with antimitochondrial antibody. The stromal component contained small round cells of bland appearance and appeared to arise from epithelial cells through a metaplastic process, as a gradual transition between epithelial and stromal cells was often seen. An invasive marginal zone of the tumor showed endometrioid adenocarcinoma pattern without any stromal component. The proliferative activity generally was low. Interestingly, it was clearly accentuated in the epithelial component especially in the peripheral invasive areas, whereas it was very low in the stromal component. The course of disease was indolent. Low-grade müllerian carcinosarcoma is to be distinguished from other biphasic müllerian tumors.