Unicentric Castleman Disease of the Mesentery Mimicking a Gastrointestinal Stromal Tumor: A Case Report.

Unicentric Castleman disease (UCD) is a rare benign lymphoproliferative disorder commonly found in the mediastinum and retroperitoneum, with mesenteric involvement being exceptionally uncommon. We present a case of a 21-year-old male with a history of constipation, fatigue, and recurrent right iliac fossa pain for six months. Initial imaging suggested a gastrointestinal stromal tumor (GIST); however, the final diagnosis of UCD hyaline vascular (HV) variant was made based on immunohistochemical (IHC) analysis and histopathological reports. Surgical excision led to complete resolution of symptoms. This unique case makes UCD a differential diagnosis for a right iliac fossa highly vascular mass and underlines the necessity for comprehensive histological and IHC analysis. Successful surgical intervention and exclusion of multicentric Castleman disease (MCD) have resulted in a favorable patient outcome.