BRCA1 and gastric cancer: Among nine genes germline pathogenic variants including APC, ATM, BRCA1, BRCA2, CDH1, MLH1, MSH2, MSH6, and PALB2 being associated with the risk of gastric cancer [43], CDKN2A had co-occurrence with MLH1, MSH6, BRCA1 and BRCA2 (Fig. 5C).