[Retroperitonal fibrosis and lymphoma in a 15-year-old boy]. / Fibrose rétropéritonéale et lymphome chez un enfant de 15ans.

Retroperitoneal fibrosis (RF) is a rare disease in children. We report the case of a 15-year-old boy who presented with a 2-month history of dorsal pain and a 2-week history of fever. The erythrocyte sedimentation rate and serum C-reactive protein value were high. Magnetic resonance imaging revealed a large heterogeneous retroperitoneal mass, suggestive of RF. Percutaneous biopsy of inguinal lymph node provided the diagnosis of anaplastic large cell lymphoma. This is the first report of RF revealing malignancy in childhood. It emphasizes that malignancy must be carefully searched for in children with unexplained RF.