Carcinosarcoma of the Female Genital Tract: Immunohistochemical study on transitional area further supports the metaplastic origin

ABSTRACT

Carcinosarcoma of the female genital tract, also called malignant mixed mullerian tumor (MMMT), is a rare and relatively aggressive tumor with various homologous and heterologous components. There have been various studies to find prognostic factors and to investigate the histogenesis, including tissue culture, electron microscopy, and immunohistochemical studies. We investigated carcinomatous, sarcomatous, and transitional areas of 6 cases of carcinosarcoma of the uterus and ovary by using epithelial and mesenchymal markers. Immunohistochemical profiles of the transitional areas were significantly different from those of carcinomatous and sarcomatous areas. Immunoreactivities for cytokeratin and epithelial membrane antigen (50% and 22.2%) were weaker than those of carcinomatous areas (95.2% and 100%), but stronger than those of sarcomatous areas (11.1% and 5.6%)(p<0.01). In transitional areas, vimentin, smooth muscle actin and S-100 protein were more strongly expressed than in carcinomatous areas, but more weakly expressed than in sarcomatous areas (p<0.01, p<0.01, and p=0.018, respectively). Myoglobin was entirely negative in carcinomatous areas and immunoreactive in minor portions of transitional and sarcomatous areas (22.2% and 16.7%, respectively). These results suggest that the transitional areas are between the carcinomatous and sarcomatous nature in differentiation, further supporting that the carcinosarcomas of the female genital tract may arise, through metaplastic change, from a type of carcinoma.