Second, based on the high percentage of CTCs that may be unidentifiable by EPCAM-based selection methods, we could see a CTC as a circulating cell, with morphology compatible with a tumor cell, showing nucleus, negativity to pan-hematopoietic marker CD45 and positivity to CK8, CK18 and CK19, regardless of EPCAM status [31]. The gene discussed is KRT18; the disease is neoplasm.