Should grade 3 endometrioid endometrial carcinoma be considered a type 2 cancer-a clinical and pathological evaluation

Objective Endometrial cancer is classified into: Type I estrogen-dependent endometrioid adenocarcinoma, with good prognosis and type 2 non-estrogen-dependent cancer with serous or clear cell histology and poor prognosis. Grade 3 endometrioid cancers (G3 EEC), share features of type 1 and type 2 cancer and have not been classified as either. This study compares immunohistochemistry and survival in G3 EEC and type 2 cancers. Methods Clinicopathological data compared with immunohistochemistry and survival in 156 consecutive patients with poor prognosis cancer—G3 EEC, uterine papillary serous (UPSC) and clear cell carcinoma (CC), sarcoma, carcinosarcoma and endometrial tumors of mixed histology. 131 (84%) datasets were complete, 25 tumors comprising sarcoma, carcinosarcoma or mixed histologies were excluded. Tissue microarray constructed and tested for estrogen receptor (ER), progesterone receptor (PR), p53 and human epidermal growth factor receptor-2 (Her-2). Results There was no significant difference in the mean age for G3 EEC (n=68) and USPC+CC (n=38), (68.01 and 67.08 respectively, p=0.697) or stage at diagnosis (p=0.384). For ER, PR, p53 and Her-2, there was no significant difference in marker positivity between G3 EEC and UPSC+CC (p=0.612, 0.132, 0.16 and 0.132 respectively). With a mean follow-up time 148months Disease specific and recurrence-free survival between G3 EEC and USPC+CC was similar (p=0.842 and 0.863). Conclusion G3 EEC and UPSC+CC share similar clinical, immunohistochemistry and poor survival. G3 EEC is better characterised as type 2 cancer and should be treated with similar adjuvant therapy to UPSC/CC.