Prognostic impact of histological grade and vascular invasion compared with tumour cell proliferation in endometrial carcinoma of endometrioid type

Aims: The relative impact of different prognostic factors is important for endometrial carcinoma patients. The aim of our study was to examine the combined value of histological grade [International Federation of Gynaecology and Obstetrics (FIGO)] and vascular invasion in comparison with tumour cell proliferation assessed by mitotic count and Ki67. The recently proposed binary architectural grade was also evaluated, in addition to age, depth of myometrial infiltration and FIGO stage in our population‐based series of 237 endometrioid carcinomas. Methods and results: The tumours were studied for several histological features, including FIGO grade, binary grade, vascular invasion, mitotic count, myometrial invasion and expression of Ki67. FIGO grade was significantly associated with all investigated histological features, including Ki67 expression. Vascular invasion was significantly more frequent in FIGO grade 3 tumours, and was associated with a diffusely infiltrative growth pattern, solid growth, necrosis and deep myometrial invasion. All variables showed a highly significant relationship with patient survival in univariate analysis. In multivariate models, FIGO grade, vascular invasion, and proliferation assessed by Ki67 expression all had independent prognostic influence in this population‐based study. Comparing tumour cell proliferation (Ki67) with vascular invasion as a marker of metastatic spread, the latter had a stronger survival impact. Conclusions: Vascular invasion and tumour cell proliferation measured by Ki67 both had independent prognostic influence, and should be considered to identify aggressive tumours of the endometrioid subtype.