Hematoxylin‐Eosin staining showed that the presence of CMTM4 in tumor tissue increased atypical cell production, and Immunofluorescence (IF) staining confirmed a significant reduction in Ki67‐ and CD44‐positive (invasive marker) regions in ID8/CMTM4 KO tumors (Figure S3E, Supporting Information). Here, CD44 is linked to neoplasm.