Solitary plasmacytoma of the submandibular lymph node with stromal amyloid deposits.

This report concerns a case of solitary extramedullary plasmacytoma of the left submandibular lymph node in a 56-year-old man. The tumor showed monoclonal proliferation of abnormal plasma cells which revealed highly positive stainings of both methylgreen pyronin and kappa light chain using the immunoperoxidase technique in the cytoplasms, and further revealed massive amyloid deposits in the stroma, which suggested the possibility of sequential amyloid formation upon the secretion of paraprotein by tumor cells.