Plasmacytoma arising in giant lymph node hyperplasia.

Giant lymph node hyperplasia (GLNH) is generally thought to represent a benign process. A patient with GLNH of the chest wall had part of the lymph node replaced by large nodules of infiltrating plasma cells, and a serum paraprotein of the IgG lambda type. A peroxidase-antiperoxidase immunocytochemical technic showed that the plasma cells within areas of typical appearing GLNH were polyclonal, whereas those making up the nodular infiltrates were monoclonal. The observation of a plasmacytoma arising in this lesion demonstrates the neoplastic potential of GLNH.