A case of Castleman disease of the retroperitoneum in a 26-year-old wo
man is presented. Sonography, computed tomography, and magnetic resona
nce imaging demonstrated a large retroperitoneal mass with somewhat he
terogeneous imaging characteristics. Although a definitive preoperativ
e diagnosis was not possible, magnetic resonance imaging was useful in
delineating the extent of the tumor and defining the characteristics
of surrounding soft tissues.