ATM and cholangiocarcinoma: Another study that involved a total of 382 patients with BTC found P/LP germline variants in moderate and high penetrance genes ATM, BLM, BRCA2, ERCC2, and RAD54L. 122A study of 188 patients with CCA found 5.8% had germline variants in ATM, BLM, BRCA2, ERCC5, MSH2, PALB2, RAD50, and XPC. 123