Mucinous Adenocarcinoma of the Endometrium Compared With Endometrioid Endometrial Cancer: A SEER Analysis

Mucinous endometrial cancer (MEC) is a rare histologic subtype of endometrial cancers. The purpose of this study is to compare the outcomes of patients with MEC with patients with endometrioid endometrial cancers (EEC), and to determine whether there are significant clinicopathologic differences between these tumors.

Surveillance, Epidemiology, and End Results (SEER) Program data for 1988 to 2009 was reviewed. Demographic and clinical data were compared. The impact of histology on survival was analyzed using the Kaplan-Meier method. Factors predictive of outcome were compared using the Cox proportional hazards model.

The study group consisted of 104,659 women, 103,097 (98.5%) had EEC and 1562 (1.5%) MEC. The mean age at diagnosis for EEC and MEC was 62 and 63.4, respectively (P<0.001). MEC tumors were more frequently classified as grade 1 (51.3% vs. 44%; P<0.001). In patients with MEC, a higher rate of pelvic lymph node metastasis (16.3% vs. 10.4%; P<0.001) was noted, but not para-aortic lymph node metastasis (5.1% vs. 4%; P=0.1). After adjusting for race, period of diagnosis, SEER registry, marital status, stage, age, surgery, radiotherapy, grade, histology, and lymph node dissection, there was no difference in survival between MEC and EEC (hazard ratio 0.90; 95% confidence interval, 0.78-1.05).

Mucinous histology does not significantly affect survival when compared with endometrioid histology in endometrial cancer. Patients with MEC were more likely to have positive pelvic lymph nodes at the time of surgery.