EVIDENCE FOR A COMMON ETIOLOGY FOR ENDOMETRIAL CARCINOMAS AND MALIGNANT MIXED MULLERIAN TUMORS

Objective. To elucidate factors linked to the development of malignant mixed mullerian tumors (MMMT) and determine whether the risk factor p rofile for these tumors corresponds with that for the more common endo metrial carcinomas. Methods. A multicenter case-control study of 424 w omen diagnosed with endometrial carcinoma, 29 women diagnosed with MMM T, and 320 community controls was conducted. Review of pathological re ports and slides was performed to classify cases by histological type. All participants were asked to respond to a questionnaire which ascer tained information on exposure to factors postulated to be linked to t he development of uterine tumors. Results. Women with endometrial carc inomas and MMMTs were similar with respect to age and educational atta inment. Women diagnosed with MMMTs were more likely than those diagnos ed with carcinomas to be of African-American descent (28% vs 4%; P = 0 .001). Weight, exogenous estrogen use, and nulliparity were related to risk of both tumor types. Marked obesity was associated with a 4.8-fo ld (95% CI = 3.0,7.6) increase in risk of carcinoma and a 3.2-fold (95 % CI = 1.1,9.1) increase in risk of MMMT development. Use of exogenous estrogens increased the odds of developing carcinomas by 2-fold (95% CI = 1.3,3.2) and that of developing MMMTs by 1.8-fold (95% CI = 0.57, 5.5). Nulliparity was associated with a 2.9-foId (95% CI = 1.9,4.8) in crease in risk of carcinomas and a 1.7-fold (95% CI = 0.53,5.6) increa se in risk of MMMTs, Oral contraceptive use protected against the deve lopment of both carcinomas (OR = 0.39; 95% CI = 0.26,0.58) and MMMTs ( OR = 0.76; 95% CI = 0.25,2.3). Current smokers were at a reduced risk of developing endometrial carcinomas (OR = 0.34; 95% CI = 0.21,0.55) a nd MMMTs (OR = 0.57; 95% CI = 0.15,2.3), while former smokers were at an increased risk of MMMT (OR = 2.7; 95% CI = 1.1,6.8) but not carcino ma development (OR = 0.81; 95% CI = 0.56,1.2). Conclusion. Results fro m this study suggest that MMMTs and carcinomas have a similar risk fac tor profile. This observation is compatible with the hypothesis that t he pathogenesis of these two histological types of uterine tumors is s imilar. (C) 1998 Academic Press.