Distinguishing from a few tumor specific biomarkers (PSA, AFP, HCG etc) [1]–[3], thymidine kinase 1 (TK1, ATP; thymidine 5′-phosphotransferase; EC.2.7.1.21) is one of the non-specific tumor markers that can be measured in continuously dividing cells [4]. Here, TK1 is linked to neoplasm.