Concurrent Development of Hepatoblastoma and Wilms Tumor in a Child with Trisomy 18

Children with trisomy 18 are predisposed to developing hepatoblastoma and Wilms tumor (WT) ; however, the simultaneous occurrence of these two malignancies in the same patient has not been previously documented. We report a rare case of synchronous hepatoblastoma and renal tumor in a child with trisomy 18. The hepatoblastoma was treated with surgical resection followed by chemotherapy. The renal lesion, initially suspected to represent intralobular nephrogenic rests, showed rapid progression and was clinically diagnosed as WT. This case underscores the increased susceptibility of patients with trisomy 18 to multiple malignancies and emphasizes the need for careful oncologic surveillance in this population. Shinshu Med J 74 : 111―116, 2026