A case of mediastinal mass grossly resembling thymoma has been shown to be a giant lymph-node hypersplasia, coexisting width some properties of the plasma cell variant. There were lymphoid follicles of hyaline-vasculer type, characterized by small germinal-centers and marked capillary prolifaretion width fibrous hyalinization. The medulla of the lymph node were occupied by large sheets of plasma cells.