A 7-year-old girl presented with 6 days of vomiting and abdominal pain in addition to a 3.5-kg weight loss over the past 6 months. On examination, she was pale and thin. Her weight was 16.9 kg (<5th percentile for age), and her height was 116 cm (10th percentile). Abdominal examination revealed a well-defined, firm, mobile, nontender, and nonpulsatile 8 × 8-cm mass in the left upper quadrant extending into the epigastric region. Laboratory studies showed a microcytic anemia with a hemoglobin concentration of 9.0 g/dL; the hematocrit was 26.8%. Amylase and lipase levels were normal. Hemoccult test results for stool and emesis were positive for blood. Abdominal radiography was performed (see Figure 1 and Figure 2).