A 20-month-old female presented with respiratory distress and a right adrenal mass extending into the inferior vena cava and right atrium. The mass was initially thought to be neuroblastoma. Pathology later revealed adrenocortical carcinoma. Inferior vena cava extension is far more common in adrenocortical carcinoma than neuroblastoma, and its presence should prompt clinical and laboratory evaluation for an adrenocortical tumor. The genetic findings in TP53 associated with this disease are discussed.