IL33 is expressed by vascular endothelial cells and tumor cells in the human colon cancer microenvironment, suggesting their important role in colon cancer. Using multiplexed immunophenotyping microscopy, Fang and colleagues found that PAN-Keratin-positive (green) tumor cells and CD31-positive (blue) vascular endothelial cells expressed IL33 (red) in primary and metastatic colon cancer tissues. When colon cancer cells were IL33-positive, the adjacent colon epithelial cells were IL33 negative. For details, see article by Fang and colleagues on page 2735.