The aim of this study was to examine the associations among the haphazard invasive patterns, defined as directionless infiltration into the myometrium; expression of key proteins; tumor infiltrative lymphocytes (TILs); and the prognosis of gade-3 endometrioid carcinoma (G3EC). Between 1990 and 2013, patients with G3EC who underwent surgery at our hospital were identified. Invasive patterns were classified into either haphazard, infiltrative, or expansile patterns. The estrogen, progesterone, androgen receptor, cytokeratin 5/6, epidermal growth factor receptor, E-cadherin, snail-2, vimentin, ZEB1, chromogranin A, synaptophysin, MLH1, MSH2, MSH6, and PMS2 levels were evaluated by immunochemical analysis. The degree of strong or weak lymphocyte infiltration (LI) were evaluated using zone formation of LI at the invasive front. Haphazard, infiltrative, and expansile patterns were discovered in 8 (18%), 6 (13%), and 31 (69%) cases, respectively. Cases with the haphazard patterns were diagnosed at a more advanced stage (p < 0.01) and recurred more frequently (p < 0.01). There were statistical differences in progression-free survival (PFS) and overall survival (OS) between the three groups (PFS; p < 0.01: OS; p < 0.01). In multivariate analysis, only the haphazard pattern was found to be an independent, worse prognostic factor of PFS (Hazard ratio (HR) =10.8, p < 0.01) and OS (HR = 23.3, p < 0.01). Furthermore, the haphazard invasive pattern was related with weak LI (p < 0.01) but not with the expression of all proteins analyzed. The haphazard pattern was found to be a worse prognostic factor and was associated with weak LI in G3EC. The aggressive feature of G3EC might be associated with LI but not tumor biology.
Keywords: Endometrial carcinoma; Endometrial endometrioid carcinoma; Invasive pattern; Tumor infiltrating lymphocyte.