Bone Marrow, Plasma cell neoplasm

Clinical history of lytic bone lesions in the thoracic and lumbar vertebrae in the elderly should prompt high suspicion for plasma cell neoplasm. This slide shows highly cellular infiltrates that are predominantly plasmacytoid. The majority of the cells are with ample basophilic cytoplasm, perinuclear hof, round eccentric nuclei. Some show “clock face” chromatin and inconspicuous nucleoli.

These cells typically show CD138 (+), CD38 (+), CD79a (+), MUM1 (+), aberrant expression of CD56 (+), and light chain restriction. They also usually show negative staining for CD19 (-), CD20 (-), PAX5 (-), CD45 (-).