Abdominal Mass Caused Failure to Thrive in a Young Boy: Mixed-Type Localized Retroperitoneal Castleman Disease.

Castleman disease is a rare cause of retroperitoneal mass in children. Clinical presentation and laboratory findings are usually nonspecific. Imaging shows features of a hypervascular or soft tissue mass. We present a 12-year-old boy who complained of frequent colds, fatigue, and failure to gain weight for the past 4 years who was referred to our hospital. Anemia and hypergammaglobulinemia were revealed in laboratory tests. Imaging showed a well-delineated retroperitoneal soft tissue mass with intense homogenous enhancement at the midline below the aortic bifurcation. The histopathological features were consistent with mixed type unicentric Castleman disease. Surgical removal was curative. Our patient's hematological abnormalities resolved, and he gained 10 kg in the next 4 weeks after the operation and reached the 25-50th percentile for his age.