cases, retroperitoneum Week 395: Case 1 April 26, 2023 pathadmin 1. Presented by Peter Illei, M.D. and prepared by Andrea Subhawong, M.D.2 year old boy with a large abdominal/retroperitoneal mass. Immunostains were positive for chromogranin and synaptophysin. Cytokeratin was negative.Neuroblastoma, undifferentiatedWilms tumorDesmoplastic small round cell tumorPNET 1. Presented by Peter Illei, M.D. and prepared by Andrea Subhawong, M.D.2 year old boy with a large abdominal/retroperitoneal mass. Immunostains were positive for chromogranin and synaptophysin. Cytokeratin was negative.