Malignant lymphoma of the parotid gland with monoclonal cytoplasmic immunoglobulin.

A 56-year-old Japanese man with a malignant lymphoma of the parotid gland was reported. The tumor was located in the superficial lobe of the parotid gland, and somewhat invaded the surrounding soft tissues, but the regional lymph nodes were not involved. Histologically, the tumor was composed of round cells with plasmacytoid configurations and small lymphocytes. The plasmacytoid cells showed eccentric nuclei with fairly marked irregularities and perinuclearr halos. In a large number of tumor cells, a monoclonal cytoplasmic immunoglobulin (CIg), IgG-Kappa type, was demonstrated by the PAP method. Ultrastructurally, some of the tumor cells showed well-developed endoplasmic reticulum. From these findings, this tumor was diagnosed as a diffuse B-cell lymphoma, mainly composed of lymphoplasmacytoid cells. And this tumor may bear a similar nature to an extramedullary plasmacytoma of the classical terminology. Malignant lymphoma of the parotid gland is rare but a case with the demonstration of monoclonal CIg is considered very rare.