Does high-grade endometrioid carcinoma (grade 3 FIGO) belong to type I or type II endometrial cancer? A clinical-pathological and immunohistochemical study

This study was aimed at determining whether high-grade endometrioid carcinomas (grade 3 International Federation of Gynecology and Obstetrics) might overlap, at least partially, non-endometrioid carcinomas (type II). To this end, a panel of clinical-pathological and immunohistochemical parameters was evaluated in three different populations: low-grade endometrioid carcinomas (LGECs; n = 57), high-grade endometrioid carcinomas (HGECs; n = 26), and non-endometrioid carcinomas (NECs; n = 30). Besides morphological appearance, HGECs appeared similar to LGECs in p53 immunostaining profile; features different from LGECs included a higher local aggressiveness, a higher invasion of lymph-vascular spaces, a lower expression of ER alpha and PR, and a higher proliferative index. HGECs were similar to NECs for local aggressiveness, invasion rate of lymph-vascular spaces, lymph node metastasis incidence, and proliferative index. HGECs, however, showed a lower rate of extra-nodal metastases, a lower incidence of p53 overexpression, and a higher positivity for ER alpha and PR. In conclusion, results from this study show that HGECs exhibit overlapping morphological and immunohistochemical features of both type I and type II endometrial carcinomas. Further research is needed to clarify the clinical value of this observation.