Clinical features of biliary tract cancer in Japanese individuals with Lynch syndrome

Background: Biliary tract cancer (BTC) is a Lynch syndrome (LS)-associated cancer with a high mortality rate. This study aimed to clarify the clinical features of BTC in individuals with LS and to discuss its management. Methods: We obtained data from genetically verified Japanese individuals with LS who were diagnosed at a single institution, between January 2003 and April 2021. Moreover, 21 individuals with sporadic BTC (n=15) and LS associated BTC (n=6) underwent microsatellite instability (MSI) testing. Results: Among 92 individuals with LS, 6 individuals with MLH1 variants developed BTCs (10 lesions, male/female, 2:1). The median age at diagnosis of initial BTC was 69 years (range, 34–78 years). Histological examination revealed a predominance of differentiated adenocarcinoma (89%). Then, 2 individuals had multiple BTCs. All available 7 BTC lesions showed high-frequency of microsatellite instability (MSI-H). MLH1 carriers showed a 7.2% cumulative risk of BTC development at an age of 70 years. Five of the six individuals died of BTC. Conclusions: MSI analysis could facilitate LS identification in individuals with BTC. Surveillance for BTC should be considered for MLH1 carriers in Japan.