‐During tumor progression peritoneal cavity macrophages proliferated and switched gradually from expressing M1 (Ccr2, Ifnar, iNOS) to M2 genes (Cd206, arginase 1, Cd163).‐Whether tumor‐associated macrophages resulted from proliferation of resident LPMs, and/or differentiated from monocytes, was not addressed. The gene discussed is ARG1; the disease is neoplasm.