Uterine malignant mixed mullerian tumors should not be included in studies of endometrial carcinoma.

Objective: Uterine mixed malignant mullerian tumors (MMMT) have traditionally been excluded from clinical trials of endometrial cancer because of a belief that they are more correctly included in the sarcoma category. Recently, investigators have suggested that uterine MMMTs are actually dedifferentiated epithelial tumors and should be treated as such. The current study was undertaken to compare outcomes, stage for stage, of uterine MMMT with poor prognosis endometrial adenocarcinomas.
Methods: Cases of MMMT from 1996 to 2004 were identified from the Tumor Registry after IRB consent was obtained. Retrospective chart review was performed. Cases were matched by age, stage, performance status, and surgical procedure to controls consisting of grade 3 endometrioid, papillary serous, and clear cell endometrial carcinomas from the same time period. Overall survival was compared using the Log-Rank test.
Results: 68 patients with MMMT were identified. 23 were excluded due to incomplete records. Patients with MMMT ranged in age from 51 to 95 years (mean 75.3 years). Approximately half of the patients (53%) had stage III or IV disease. Of the controls, 31 (69%) had grade 3 endometrioid, 11 (24%) papillary serous, and 3 (7%) clear cell carcinoma. Median overall survival for all patients with MMMT was significantly shorter than for controls, 18 months (range 0.5-72) versus 36 months (range 0.5-123) (P = 0.02). Patients with early stage disease (stage I or II) had shorter median survival than controls, 26 months (range 3-7) vs. 95 months (range 4-123) (P = 0.003). There was no difference in median survival when comparing advanced disease (stage III or IV) to matched controls, 15 months (range 0.5-70) vs. 19 months (range 0.5-100) (P = NS).
Conclusions: Patients with uterine MMMT have a poorer prognosis than those patients with high grade epithelial tumors, especially for those with early stage disease. Given the discrepancy in survival, these patients should not be included in studies of endometrial carcinoma. Further investigations are necessary to identify factors to improve survival of these patients.