Mixed Müllerian Tumors of the Female Genital Tract.

Malignant mixed müllerian tumor (MMMT) and müllerian/mesodermal adenosarcoma are 2 of the most common mixed müllerian tumors of the female genital tract. MMMT is a biphasic neoplasm, composed of morphologically malignant epithelial and stromal components. MMMT should be distinguished from endometrioid adenocarcinoma with spindle cell elements, "dedifferentiated" endometrioid carcinoma, and combined adenocarcinoma and neuroendocrine carcinoma. Adenosarcoma is also biphasic; it is composed of morphologically benign or low-grade appearing epithelial components and malignant stromal components. The differential diagnosis of adenosarcoma includes MMMT, endometrial stromal tumor containing endometrioid glands, benign endometrial or endocervical polyp, adenofibroma, adenomyoma, including atypical polypoid adenomyoma, botryoid embryonal rhabdomyosarcoma (sarcoma botryoides), and endometriosis, including polypoid endometriosis. Gross and microscopic features, including immunophenotype, should permit discrimination of the various entities.