KRT18 and cancer: In situ Phenotyping and karyotyping CTCs (in situ PK CTC) by i•FISH® demonstrated the majority of CTCs identified in patients (Figures 2C and 2L, 4) or the most cancer cell line CTCs in mouse blood in this study (Figure 2N) had no detectable or visible CK18 or PanCK including CK4, 5, 6, 8.