Introduction/Background Endometrial cancer (EC) is the most commonly diagnosed gynecologic malignancy among women worldwide and may be classified on the basis of different molecular, pathologic and genetic alterations, including microsatellite instability (MSI). Although MSI is associated with a more favorable outcome in colorectal cancer, its relationship with prognosis in EC cancer is not yet clear.

Methodology 100 primary endometrioid type endometrial carcinoma cases, surgically staged in Ege University Gynecological Oncology Department, were included in the study. The files of the patients who applied between 2002–2016 were searched. A tumor sample was defined as MMR deficiency (dMMR) with a loss of at least one of the MMR proteins. The cases were divided into two groups as MMR-deficiency and MMR-proficient. The cases were compared in terms of prognostic factors with loss of nuclear expression in MMR proteins by IHC method. The effects of these parameters on survival were examined.

Results According to the FIGO 2009 staging system, the patients included in the study were distributed as stage I patient group 77 (77%), stage II 14 (14%), stage III 8 (8%), stage IV 1 (1%). Twenty-eight (28%) of the cases were found to be grade 1, 57% grade 2, and 15% grade 3. There was no statistically significant difference between the dMMR and MMR-proficient groups in terms of age, menopausal status, family history, need for adjuvant treatment, recurrence, mortality, FIGO stage, grade, adnexal involvement, lymph node involvement and tumor size (p>0.05). LVSI was more common in the dMMR group than in the MMR-proficient group (p=0.020, respectively). In addition, deep myometrial involvement was less common in the dMMR group compared to the MMR-proficient group (p=0.002, respectively).

Conclusion As a result, in endometrioid type endometrial cancers, a significant relationship was found between MMR and lymphovascular space involvement and deep myometrial invasion. However, there was no effect on survival.

Disclosures The aim of our study is to reveal the molecular features of endometrial cancer by immunohistochemical (IHC) method and to determine their relationship with prognostic variables.