This is, to our knowledge, the first population-based study to quantify the cancer risk in children with BWSp with IC1-LOM, IC2-GOM, UPDpat, deletions/duplications and pathogenetic variants in CDKN1C. We observed a significant excess risk for all childhood cancers combined compared with the general population. Here, CDKN1C is linked to childhood malignant neoplasm.