Loss of hMLH1 expression is associated with less aggressive clinicopathological features in sporadic endometrioid endometrial adenocarcinoma

Aim: To assess the incidence and clinicopathological significance of microsatellite instability (MSI) and the protein expression of hMLH1 and hMSH2 in sporadic endometrioid endometrial adenocarcinoma (SEEA). Methods: A total of 50 patients with pure endometrioid sporadic endometrial adenocarcinoma were enrolled in the study. MSI analysis was done using five polymorphic markers (BAT26, D5S346, BAT25, D17S250, D2S123) and the protein expression of the hMLH1 and hMSH2 genes was determined by immunohistochemical staining. MSI was detected in 24% (12/50) of SEEA cases. Results: There was a significant correlation between MSI status and loss of hMLH1, hMSH2 expression, respectively. No significant association was found between MSI status and clinicopathological parameters, including age, grade, stage, depth of myometrial invasion, lymph-vascular space invasion (LVI), lymph node involvement or peritoneal cytology. However, significant correlations were found between loss of hMLH1 and a lower histological grade and the absence of LVI in patients with SEEA. Conclusions: According to these results, MSI and a loss of protein expression of hMLH1 and hMSH2 may be associated with the pathogenesis of SEEA. In addition, hMLH1 immunostaining might have a role as a prognostic parameter. Further research using a large number of cases is needed to confirm our observations.