Background: Multiple factors linked to etiology, clinical course and prognosis in to types of endometrial cancer  endometrioid type I and non-endometrioid type II cancer  have been recognised .These include alterations in concentrations of estrogen and progesterone hormones, mutations in MMR  mismatch repair  genes, PTEN, TP53, beta-catenin, disturbed signalling pathays  e.g. PI3KAKT . Hoever, in several studies, including the data of Epidemiology of Endometrial Cancer Consortium, endometrial cancers and those of type II  serous carcinoma and clear-cells carcinoma  in particular proved to be more heterogenous than expected  1 ,-2, 3 . Methods: The study manifested a multi-centre character. Using sections of paraffin-embedded preparations and immunocytochemistry ith application of specific antibodies, in 115 patients ith EC type I and in 31 patients ith EC type II, the expression of ER xDF;1, ER x2202;, PR and BRCA1 as estimated. Results: Expression of ER xDF;1 as augmented in USC  type II  , in cancers of a poor differentiation G3 , it as more pronounced in cancers of an increased clinical advancement according to FIGO. Expression of ER x2202; as detected in the endometrioid type I cancer manifesting good histological differentiation  G1or G2  and a lo clinical degree of advancement according to FIGO. In over 50 percent cases of EC type II a mutation as detected in BRCA1, associated ith a decreased expression of ER x2202;. Conclusions: An augmented expression of ER xDF;1 in EC as linked to poor prognosis in type II EC. Higher expression of ER x2202; in type I EC of increased maturity as associated ith a good prognosis. It seems that type II EC is partially connected to BRCA1 mutation.,J Clin Oncol 34, 2016  suppl; abstr e17118 ,Publication Only Gynecologic Cancer