MPO and colorectal carcinoma: MPO+ and CD15+ infiltration, as evaluated by absolute cell numbers, was significantly higher in MMR deficient than in MMR proficient CRC (median: 30 cells/punch in deficient vs. 21 cells/punch in proficient CRC P = 0.007 and 9 cells/punch in deficient vs 6 cells/punch in proficient CRC P = 0.05, for MPO and CD15 respectively; figures 2E–F).