APC and polyposis: In this report, we present the clinical case of a 35-year-old patient exhibiting multiple tumours, an aggressive course, whose genetic analysis revealed a germinal mutation in CHEK2 gen, somatic JAK2V617F and a germinal novel variant in Adenomatous Polyposis Coli (APC) gene of uncertain significance may account for the polyposis and medulloblastoma in the patient, given the variant's genomic location.