An extracellular body of plasma cell origin in inflammatory infiltrates within the dermis

Abstract

During examination of a biopsy specimen of skin by conventional microscopy, numerous round, basophilic, extracellular bodies suggestive of fungal organisms were seen in the dermis. Further evaluation and special staining suggested that their origin was from the plasma cells. Examination of biopsy material from 48 patients with cutaneous plasma cell infiltrates revealed similar bodies in 20 cases (42%). Sizes of bodies varied, the largest being 5.0 microns in diameter. In every case, staining reactions were identical to those of plasma cell cytoplasm. Immunoperoxidase methods showed that, like plasma cells, the bodies contained either kappa or lambda light chains. In one case of plasmacytoma associated with multiple myeloma, both the bodies and the surrounding neoplastic cells stained for kappa chains only. Electron microscopy revealed rounded structures composed of aggregates of rough endoplasmic reticulum, which contained varying amounts of moderately electron-dense material within the cisternae. Fragmented plasma cells were also seen. The evidence suggests that plasma cell bodies are distinct from Russell bodies. They probably form as a result of trauma during processing of tissue, but could also represent a degenerative process in vivo. They should be distinguished from pathogenic micro-organisms and other extracellular bodies.