[A Resected Case of Castleman's Disease That Was Difficult to Diagnose Preoperatively].

A 70-year-old man was referred to our hospital and admitted after abdominal computed tomography(CT)examination revealed a tumor in the retroperitoneum. The specific blood test findings were poor, and surveillance CT demonstrated a wellcircumscribed, enhanced mass measuring 40mm with calcification behind the horizontal portion of the duodenum. The tumor presented with a slightly high signal in low signal, T2 in T1, and it showed a diffusion decrease in DWI; the simple abdominal MRIrevealed heterogeneous accumulation of SUVmax 3.0 only for the lesion in FDG/PET-CT. Specific findings did not lead to a diagnosis, although EUS-FNA lower aspiration biopsy cytology was performed. Laparoscopic tumorectomy was performed to help determine the treatment strategy. Histopathological examination indicated that the tumor was composed of multiple lymph follicles with concentric layers of mantle zone cells, showing an onion skin-like lesion and atrophic germinal centers. The germinal centers had penetrating arterioles with hyalinized vessel walls, and Castleman's disease(hyaline vascular type)was therefore diagnosed. In this case, it was difficult to diagnose Castleman's disease before surgery. Surgical excision is a diagnostic as well as a curative method for management of this disease.