We aimed to assess the incidence and clinicopathologic significance of microsatellite instability (MSI) and to analyze the loss of protein expression of hMLH1, hMSH2 and Bax gene in endometrioid endometrial adenocarcinoma.

A total of 30 patients with pure endometrioid type of endometrial adenocarcinoma were examined. MSI analysis was done using five polymorphic markers (BAT26, D5S346, BAT25, D17S250, D2S123) and the protein expression of hMLH1, hMSH2 and Bax gene was determined using immunohistochemical staining.

MSI was detected in 30% (9/30) of endometrioid endometrial adenocarcinoma. There was a significant correlation between MSI status and loss of hMLH1, hMSH2 and Bax expression (p<0.05). No significant association was found between MSI status and clinicopathologic factors, such as age, grade, stage, depth of myometrial invasion, lymph- vascular space invasion, lymph node involvement and peritoneal cytology (p>0.05). But there were significant correlations between loss of hMLH1 and histological grade and lymph-vascular space invasion of endometrial adenocarcinoma (p<0.05). No significant association was found between hMSH2, Bax and clinicopathologic factors (p>0.05).

According to the results, MSI and loss of protein expression of hMLH1, hMSH2 and Bax could be associated with the pathogenesis of sporadic endometrioid endometrial adenocarcinoma. In addition, hMLH1 might have a role as a prognostic parameter. Further prospective study with a large number of cases is needed in future.