Natsuko Inagaki, Yoshiya Yamauchi, Sawako Matsumoto, Sakiko Naito, Masato Bingo, Hourin Cho, Yuri Ueda, Jingyi Dong, Kazuyo Kiribayashi, Akiko Yamamoto, Aoi Sukeda, Toshitaka Nagao, Takashi Ishikawa, Atsushi Sofuni, Takao Itoi
We report a case of BRCA1/BRCA2 double heterozygosity-a rare condition with an estimated prevalence of fewer than 1 in 100,000 individuals in unselected populations-identified through tumor genomic profiling in a 50-year-old Japanese woman with intrahepatic cholangiocarcinoma and no prior cancer history. Germline testing confirmed BRCA1 c.2389_2390del and BRCA2 c.5621_5624del. This case demonstrates that intrahepatic cholangiocarcinoma can be a sentinel malignancy of BRCA-related cancer predisposition, thus underscoring the importance of germline testing.