A 67-year-old woman had a history of melena for 7 days and a sudden onset of lower abdominal pain 2 days earlier. The bowel sounds were normal, and the abdomen was soft and dull upon percussion. However, tenderness and rebound tenderness in the lower abdomen were revealed. No abnormal findings were found throughout laboratory tests except decreased hemoglobin (7.5 g/dL). Postcontrast computerized tomography scan of the abdominopelvis showed a heterogeneously enhanced, exophytic, round mass...