High-stage endometrioid carcinoma of the ovary. Prognostic significance of pure versus mixed histologic types.

We retrospectively reviewed 80 cases of endometrioid carcinoma of the ovary: 68 pure endometrioid tumors and 12 predominantly endometrioid carcinomas (> 50%) mixed with either papillary serous or undifferentiated carcinoma. Each group had 11 cases of stage III or IV tumors, which were studied to determine whether the overall prognosis was affected by grade, histology, number of mitoses, residual tumor after surgery, and patient's age. Prognosis was significantly affected only by a mixed histologic pattern. The 5- and 10-year survival rates and the median survival time for pure endometrioid carcinomas were much better than those for mixed endometrioid carcinomas (63% and 45% and > 86 months versus 8% and 0% and 18 months, respectively). Recurrent tumors in cases of mixed endometrioid carcinoma were pure serous or undifferentiated carcinomas, whereas those in cases of pure endometrioid carcinoma were either endometrioid or high-grade carcinoma. Our results show that the presence of even a small component of serous or undifferentiated carcinoma in an otherwise predominantly endometrioid carcinoma significantly affects the prognosis. Thus pathologists should thoroughly sample all endometrioid carcinomas, especially high-stage tumors, to ensure that no serous or undifferentiated component is present.