This could be explained by shared well-known risk factors due to the special anatomy such as sclerosing cholangitis between these 2 malignancies16,17 and the same cancer-associated genes such as kirsten rat sarcoma viral oncogene homolog, tumor protein p53, NAT2, and human epidermal growth factor receptor 2.6,18–21 We also observed significant associations between colon, stomach, uterus (endometrial) cancers, and CCA, especially in younger age groups. Here, NAT2 is linked to cholangiocarcinoma.