After blocking by 4% Block Ace (DS Pharma Biomedical, Tokyo, Japan), sections were incubated with primary antibodies as follows: anti-human IL-34 antibody (1:200 dilution, clone 1D12, Millipore, MABT493), anti-human melanoma antibody (1:50 dilution, Abcam ab732), anti-human CD163 antibody (1:200 dilution, BIO-RAD MCA1853T) at 4 °C overnight. Here, IL34 is linked to melanoma.