In CRC, IL-34 expression correlated with the content of CD163, a marker of TAMs and our data indicated that tumour-infiltrating cells responded to IL-34 by up-regulating not only CD163 but also CD206, another marker of M2, and IL-6, a cytokine that activates proliferative and survival signals in CRC cells (Figure 2) (13, 44). The gene discussed is MRC1; the disease is colorectal carcinoma.