Abstract
Clinicopathological ultrastructural, and immunohistochemical findings of a new case of IgG1 heavy chain disease are reported in detail. The abnormal protein lacks the VH and CH1 region with sequence starting at 225 residue. The main pathologic feature was plasmacytic tumor of the lymph nodes with B-cell immunoblastic sarcoma patterns. Neoplastic diffusion to other organs was also present. Plasmacytic neoplastic cells have also been found in the bone marrow. The ultrastructure of the noeplastic cells was characterized by more or less abundant plasmacytic-like endoplasmic reticulum with very frequent peculiar whorled configurations. Immunohistochemical methods revealed the abnormal protein production by neoplastic cells in different stages of differentiation. From this case and from the data of the literature it is concluded that the gamma HCD is due to a neoplastic proliferation of lymphoplasmacytic cells whereas the reticulum cells are never involved.