Plasma cell neoplasms

**Definition:** Plasma cell neoplasms are a group of disorders characterized by the monoclonal expansion of terminally differentiated B cells (plasma cells) that produce monoclonal immunoglobulins, known as M proteins or paraproteins. Key types include plasma cell myeloma (multiple myeloma), plasmacytoma, and neoplasms associated with paraneoplastic syndromes like POEMS syndrome.