Unicentric Castleman disease is a rare condition of lymphoid hyperplasia, of which only 15% of cases occur in the abdomen. We report a 66-year-old man who presented with complaints of abdominal pain. Computed tomography scans revealed nephrolithiasis and a homogeneous calcified mass between the pancreas and stomach and several para-pancreatic nodes. Direct visualization during exploratory laparotomy revealed a mass on the lesser curvature of the stomach. Pyloromyotomy and mass resection were performed. Biopsy showed reactive lymphoid hyperplasia consistent with the hyaline vascular variant of Castleman disease.