Keratin, type I cytoskeletal 8 also known as cytokeratin-8 (CK-8) or keratin-8 (K8) is a keratin protein that in human is encoded by the KRT8 gene. It is often paired with keratin 18. Antibodies to CK8 (e.g. CAM 5.2) can be used to differentiate lobular carcinoma of the breast from ductal carcinoma of the breast. Keratin 8 is often used together with keratin 18 and keratin 19 to differentiate cells of epithelial origin from hematopoietic cells in tests that enumerate circulating tumor cells in blood. Alternative Names: Keratin K 8, Keratin K-8 protein, Keratin K8, CK8 protein, CARD2 protein, KO protein, Cytokeratin 8 protein, K8 protein, KRT8 protein, CYK8 protein, Keratin K 8 protein, Keratin 8 protein, K2C8 protein, Keratin K-8