Developed engineered macrophages by coupling luciferase expression to activation of the Arginase-1 promoter, resulting in luminescence production when macrophages adopt an M2 tumor-associated phenotype. Engineered macrophages were injected into tumor-bearing and control mice and luciferase was measured in the blood. 100% sensitivity and specificity were obtained for discriminating cancer from healthy mice. This evidence concerns the gene ARG1 and neoplasm.