Fig. 1

HVV unicentric Castleman disease in a 26-year-old woman. Axial non-enhanced (a), arterial phase (b), and portal venous phase (c) computed tomography images of the abdomen depict a well-defined heterogeneous mass of soft-tissue density (*) with branched calcification at the pancreatic head (arrowhead), which shows progressive enhancement, slightly greater than that of the pancreas. The feeding artery (black arrow) and draining vein (white arrow) can be seen. Photomicrograph (d, original magnification, × 200; hematoxylin-eosin [H-E] staining) shows marked vascular proliferation and hyalinization of the abnormal germinal center, with a tight concentric layering of lymphocytes at the periphery of the follicle, resulting in an “onion-skin” appearance (open arrow) and vessel-rich interfollicular stroma (arrowhead). (UCD = unicentric Castleman disease; MCD = multicentric Castleman disease; HVV = Hyaline vascular variant; PCV = Plasma cell variant)