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. Here, CHEK2 is linked to medulloblastoma.