A 4-YEAR-OLD girl with no noteworthy medical history presented to the emergency department complaining of right arm pain after falling off a swing. A nondisplaced transverse fracture of the proximal right humerus was discovered on initial radiographs. On subsequent physical examination, a large abdominal mass was palpated. A plain radiograph of the abdomen demonstrated a masslike density in the left upper quadrant with inferior displacement of the transverse colon and medial displacement of the stomach bubble. Calcifications were noted on the plain radiograph. A computed tomographic scan of the abdomen was immediately obtained (Figure 1 and Figure 2).