Prevalence and Molecular Characterization of Defective DNA Mismatch Repair in Small-bowel Carcinoma in a Japanese Hospital-based Population

• Main Authors: Tetsuya Ito, Hideyuki Ishida, Okihide Suzuki, Noriyasu Chika, Kunihiko Amano, Keiichiro Ishibashi, Nao Kamae, Yuhki Tada, Kiwamu Akagi, Hidetaka Eguchi, Yasushi Okazaki
• Format: Article
• Language: English
• Published: The Japan Society of Coloproctology 2020-10-01
• Series: Journal of the Anus, Rectum and Colon
• Subjects: small-bowel carcinoma; dna mismatch repair; lynch syndrome; microsatellite instability; universal tumor screening
• Online Access: https://www.jstage.jst.go.jp/article/jarc/4/4/4_2020-026/_pdf/-char/en

Objectives: To investigate the prevalence and molecular characteristics of defective DNA mismatch repair (dMMR) in small-bowel carcinoma (SBC) in a Japanese-hospital population. Methods: Immunohistochemistry was performed to evaluate the expression of MMR proteins (MLH1, MSH2, MSH6, and PMS2) in formalin-fixed paraffin-embedded sections prepared from surgically resected primary SBCs from 30 patients during March 2002 to March 2017. Genetic testing for Lynch syndrome was performed in patients who demonstrated MMR protein loss. Results: Two of 30 patients (6.7%) demonstrated concomitant loss of MSH2/MSH6 protein expression. Further genetic testing identified a pathogenic MSH2 variant in one of these patients. Conclusions: The prevalence of dMMR SBCs in a Japanese hospital-based population seems lower than that reported in previous studies. To determine whether dMMR SBCs might be strongly linked to Lynch syndrome, there is a need for further investigation with a larger sample size.