Gastric plasmacytoma with cylindrical crystalline inclusions

An 81 year-old female case of extramedullary plasmacytoma of the stomach is reported. Immunohistochemically, the tumor cells contained IgM-lambda immunoglobulin. Electron micrographs of the tumor cells showed centrally located nuclei with nuclear inclusions and cytoplasm filled with crystalline inclusions in the rough endoplasmic reticulum. IgM-lambda producing gastric plasmacytoma with cylindrical inclusions is rare.