Ovarian malignant Mullerian mixed tumor (heterologous) whose epithelial component is composed predominantly of signet ring cell carcinoma

Ovarian malignant Mullerian mixed tumor (MMMT) (carcinosarcoma) is a relatively rare, very aggressive tumor.

Herein is presented an unusual case of heterologous MMMT with an epithelial element composed predominantly of signet ring cell carcinoma.

A 60-year-old Japanese woman consulted our hospital because of a pelvic mass. Imaging modalities showed a huge tumor of the right ovary. Laparotomy was performed, and frozen section showed a malignant tumor. Therefore, hysterectomy, bilateral salpingo-oophorectomy, lymph node dissection, and omentectomy were performed. On gross examination, the right ovarian tumor was solid, measuring 12 × 13 × 12 cm. The surface was smooth but bosselated. Histologically, the tumor was composed of epithelial and sarcomatous elements. Curiously, the epithelial element was composed predominantly of signet ring cell carcinoma. A small area showed tubular adenocarcinoma and poorly differentiated carcinoma. The sarcomatous element was homologous with spindle cell sarcoma with many mitotic cells. The signet ring cells had mucins. Immunohistochemically, the epithelial element was positive for cytokeratins, EMA, p53, CEA, CA19-9, and Ki-67 (labeling = 75%). The sarcomatous element was positive for vimentin, α-smooth muscle actin, p53, and Ki-67 (labeling = 36%), indicating that it was a leiomyosarcoma. Metastases were found in many lymph nodes and intravascular spaces in the peritoneum; the metastases were composed of epithelial elements.

To the best of our knowledge, there have been no descriptions in the English literature of MMMT composed predominantly of signet ring cell carcinoma. An MMMT in this case, should be differentiated from Krukenberg tumor, metastatic signet ring cell carcinoma, and signet ring stromal tumor.