CA12 and nonpapillary renal cell carcinoma: ROC curve evaluations of two groups of CTCs (CAXII S+ vs. CK+ (either CK S+ or DP)) revealed that the number of CK+ CTCs (2.6/mL optimal cutoff) significantly correlated with radiographic progression (P < 0.05), whereas the number of CAXII S+ CTCs did not (P > 0.05) (Fig. 2E and F), demonstrating the value of considering CTC heterogeneity in ccRCC CTC diagnostics.