The stroma-rich variant of the hyaline-vascular type of Castleman's disease is a rare disease entity that is characterized by the overgrowth of a variety of stromal cells in the widened interfollicular area. We report a case of a 21-year-old woman who was admitted with a retroperitoneal mass that was initially suspected to be a liposarcoma, malignant fibrous histiocytoma or neurogenic tumor, but later confirmed as the stroma-rich variant subtype of Castleman's disease. Preoperative computed tomography (CT) and magnetic resonance imaging (MRI) showed an arborizing pattern of central calcifications and centrifugal contrast enhancement pattern of the mass. Herein, we discuss the MRI findings of this stroma-rich variant subtype.