TACSTD2 and cancer: Trop-2, N-Cadherin, CD 138, CD 318, protein receptor, MSC, Twist, mammaglobin, HER-1,2,3 and 4, etc. The difference in the concentration of CTCs among cancers from different organs and the heterogeneity of CTC-markers makes it difficult to determine how many biomarkers will be optimal for general or organ-specific tumor detection.