RESUMEN
BACKGROUND Castleman's disease is a benign, lymphoproliferative disorder that is extremely uncommon. Multiple classifications have been described; however, the exact etiology remains unknown. Preoperative diagnosis is not common, as imaging cannot distinguish the disease from other processes, and biopsy is insufficient to provide the architecture of the mass, which is necessary for diagnosis. Unicentric retroperitoneal disease has been described, and management includes complete resection of the mass, which is usually curative. CASE REPORT A 34-year-old previously healthy woman presented with hematuria. Evaluation revelated a retroperitoneal mass that was abutting the duodenum and head of the pancreas. Biopsy failed to provide a diagnosis, so laparoscopic resection was performed. Postoperative diagnosis was consistent with unicentric Castleman's disease. CONCLUSIONS Castleman's disease is an uncommon process, and one that is difficult to diagnose. Unicentric Castleman's disease should always be a differential diagnosis of solitary retroperitoneal masses that are well-demarcated, as treatment can be curative with surgical resection.