Several previous studies have compared the expression of EGFR, HER2, or HER3 between primary and distant metastatic lesions of CRC, and the correlation rates ranged from 46.5 to 94.7% for EGFR (46.5%16, 94.7%17, and 60%18), and from 55 to 72.7% for HER2 (55%18, 72.7%19, and 70.2%20). The gene discussed is ERBB2; the disease is colorectal carcinoma.