EGFR expression on CTCs of colorectal, prostate, non-small cell lung, gastric, head and neck, and breast cancer [32, 36, 121, 210, 283, 285–288]Treatment resistance T790M EGFR mutation in CTCs of non-small cell lung cancer [289]Lapatinib treatment of metastatic breast cancer patients with EGFR-positive CTCs [290]EGFR is part of the signature of breast cancer CTCs competent for brain metastases [284]. The gene discussed is EGFR; the disease is breast carcinoma.