RAD51D and cholangiocarcinoma: Concerning the frequency of individual HRR-related gene mutations in CCA cell lines, ARID1A mutations were most prevalent (5/12, 42%), followed by BRCA2, CHEK2, BARD1 (2/12, 8% each), and BAP1, BRCA1, BRIP1, FANCA, FANCD2, FANCE, FANCF, PALB2, RAD50 and RAD51B and RAD51D (1/12, 8% each).