Clinicopathologic Correlation of Mucinous Differentiation in Primary Ovarian Endometrioid Adenocarcinoma

Ovarian endometrioid carcinoma (OEC) and ovarian mucinous carcinoma (OMC) have different prognoses, with OMC being significantly worse. OEC can have squamous, mucinous, and tubal differentiation. Recent studies of mucinous differentiation (MUCdiff) in uterine EC disagree on the association of MUCdiff and clinical outcomes. The purpose of this study is to correlate the presence of MUCdiff in OEC with clinicopathologic features and overall survival. Forty-one cases of primary OEC (1996–2017) were reviewed. MUCdiff was defined as the presence of cells with intracellular mucin within the primary tumor. Two pathologists reviewed the cases for histologic subtype, tumor grade, size, laterality, LVI, lymph node/extranodal metastasis, and presence of mucinous differentiation. The mucinous component was quantified as <5%, 5% to 25%, and 26% to 50% of the tumor. A retrospective chart review evaluated a variety of clinical and demographic attributes. Data were analyzed using the Fisher exact test, standard Student t test analysis, and Kaplan-Meier method. MUCdiff was found in 24% (n = 10) of the cases. MUCdiff was associated with low grade, FIGO 1 (P = .0385). No patient with high-grade OEC demonstrated MUCdiff (P = .003). MUCdiff was associated with larger tumors (P = .032), higher serum levels of CA 125 (P < .001) and CA 19-9 (P < .001). There is a trend toward MUCdiff in patients with higher weight (P = .054) and BMI (P = .091). Patients with a history of endometriosis were more likely to have MUCdiff, and tumors with MUCdiff were more likely to arise within endometriosis (P = .048 and P = .025). There was no significant difference in OS between pure EC and EC with MUC diff. In ovarian EC, MUCdiff appears to be associated with low-grade features, larger tumors, endometriosis, and higher serum markers and shows a trend toward higher BMI. No significant differences in clinical outcomes were seen.