ERBB2 and breast cancer: On the other hand, CDK12 was the most common co-amplification gene with ERBB2 in breast cancer (59/80, 73.8%, Figure 3E), stomach cancer (37/83, 44.6%, Figure 3F), biliary tract cancer (33/57, 57.9%) (Figure 3G) and colorectal cancer (33/55, 60%, Figure 3H).