Endometrial endometrioid carcinoma, grade 1, is more aggressive in the elderly than in the young

Aims: The aim of this study was to characterise grade 1 (G1) endometrioid carcinoma in the elderly, by using clinicopathological features and immunohistochemical features of surrogate markers of molecular subtypes. Methods and results: We retrospectively analysed tumour samples from 268 patients with G1 endometrioid carcinoma (<40 years, n = 24; 40–59 years, n = 169; ≥60 years, n = 75) for whom long-term clinical follow-up data were available. G1 endometrioid carcinoma in the elderly (≥60 years) was characterised by frequent deep myometrial invasion, less frequent endometrioid intraepithelial neoplasia (EIN), lack of benign hyperplasia (BH), less frequent squamous differentiation, and occasional aberrant p53 expression. In contrast, this condition in the young (<40 years) was characterised by frequent EIN, BH, and squamous differentiation. Univariate analysis revealed that elderly status (≥60 years), International Federation of Obstetrics and Gynecology (FIGO) 2009 stage and aberrant p53 expression were significantly associated with shorter progression-free survival, and multivariate analysis revealed that elderly status and FIGO 2009 stage were independently associated with a poor prognosis. Conclusions: G1 endometrioid carcinoma in the elderly is more aggressive than that in the young, and elderly status is an independent predictor of shorter progression-free survival in this condition. We propose that type 1 tumours can be subdivided into type 1a (young age at onset and indolent) and type 1b (old age at onset and relatively aggressive).