Microsatellite Instability in Lung Adenocarcinoma

Abstract

Background: Lung cancer is the most common cause of cancer-related mortality worldwide. Microsatellite instability has been shown as a prognostic factor in many tumor types in recent years. In this study, we investigated the incidence and prognostic effects of MSI in lung adenocarcinomas.

Methods: Thirty-four lung resection cases diagnosed as adenocarcinoma between 2011 and 2016 were included in the study. MLH1,MSH2,MSH6 and PMS2 antibody, which are Mismatch repair proteins(MMR) were applied immunohistochemically to all cases and  the relationship between MMR protein expression and clinical parameters was investigated.

Results: As a result of immunohistochemical study, MLH1 expression was seen in 31 (91.2%), MSH 2 and MSH 6 expressions were seen in 32 cases (94.1%) and PMS2 expression was seen in 27 cases (79.4%). Loss of expression of MLH1, MSH2, MSH6 and PMS2 were detected in 3 (8.8%), 2 (5.9%), 2 (5.9%) and 7 (20.6%) patients, respectively. With these findings, 27 tumors (79.4%) expressing all MMR proteins were accepted as microsatellite stable (MSS), and 7 tumors (20.6%) were accepted as microsatellite unstable (MSI). Between the MSS and MSI groups, lymphovascular invasion (p=0.549), lymph node metastasis (p=0.442), presence of metastasis (p=0.289), pathological T stage (p=0.412) and clinical stage (p=0.10) were statistically significant no difference. The 5-year survival rate was 42% in MSI group and 40% in MSS group (p=0.875).

Conclusion: As a result of the study, no prognostic relationship was found between MSI and pathologic and clinical stages of lung adenocarcinomas, presence of lymph node and distant metastasis, presence of lymphovascular invasion and no effect on overall survival.