Non-secretory IgA kappa myeloma with distended endoplasmic reticulum: a case report.

A case of non-secretory multiple myeloma is presented. Plasma cells showed abundant cytoplasmic colloid contained in distended rough endoplasmic reticulum. Uniform cytoplasmic positivity for IgA heavy- and kappa light-chains was demonstrated with the immunoperoxidase staining technique. It is proposed that distension of the endoplasmic reticulum by immunoglobulin-related proteins is indicative of a block in their excretion or of the presence of active synthesis of the immunoglobulins or their subunits.