Mucinous histology is a risk factor for nodal metastases in endometrial cancer

Mucinous adenocarcinoma of the endometrium (MUC) is a rare histological variant of endometrial carcinoma accounting for 1-9% of endometrioid tumors. Few studies have characterized its clinical behavior. This is a case-control study at a single institution comparing the risk factors and clinical course of MUC relative to endometrioid adenocarcinoma.

A case-control study was performed including patients treated for endometrial cancer between 1996 and 2006. 41 cases of mucinous adenocarcinoma were identified. Each case was matched with two controls of endometrioid histology by age and histological grade. Cases and controls were compared with regard to known risk factors for endometrial cancer and the extent of disease at diagnosis. Chi-square tests were used to compare proportions and Student's t-tests for the comparison of means. Multivariate regression was used to identify the independent predictors of lymph node metastases. Overall survival was calculated using the Kaplan-Meier method and compared with the Log-rank test. p<.05 was considered significant for all tests.

Cases and controls were matched by age and FIGO grade and were found to be similar in regard to ethnicity, body mass index and medical history. No significant difference in myometrial invasion (MI)>50% or the presence of lymph-vascular space invasion was found between cases and controls, however, 17% of patients with MUC had lymph node metastases compared to 3% of controls (p=.01). Multivariate analysis controlling for both tumor grade and depth of MI identified mucinous histology as an independent predictor of lymph node metastasis (p=.02). There was no difference in adjuvant treatment, recurrence rate or survival between the two groups.

Mucinous differentiation was found to be an independent predictor of lymph node metastasis in the study population. Comprehensive surgical staging including retroperitoneal node dissection should be strongly considered in all endometrial cancer patients with predominantly mucinous histology.