Presacral Unicentric Castleman Disease: A Rare Malignancy Mimic

Castleman disease is a rare benign lymphoproliferative disorder, with presacral involvement being exceptionally uncommon. We report a 25-year-old male who presented with abdominal distension and progressive constipation. Contrast-enhanced computed tomography (CT) demonstrated a 7.7 cm hypervascular presacral mass with intense heterogeneous arterial enhancement, persistent delayed enhancement, and intralesional calcifications. Magnetic resonance imaging revealed diffusion restriction, prominent internal flow voids, and preservation of adjacent tissue planes without sacral invasion. Fluorodeoxyglucose positron emission tomography-CT (FDG PET-CT) showed only low-grade metabolic activity (SUVmax 4.1). Based on the imaging findings, differential considerations included mesenchymal neoplasm and extra-gastrointestinal stromal tumor. Surgical exploration revealed a highly vascular, encapsulated mass, and histopathological examination confirmed unicentric hyaline-vascular Castleman disease. The imaging features closely mirrored those described in previous reports of retroperitoneal Castleman disease, highlighting its potential to mimic aggressive mesenchymal tumors. Recognition of characteristic findings, including marked hypervascularity, feeding vessels, calcification, diffusion restriction, and relatively low FDG uptake, may facilitate preoperative diagnosis and surgical planning.