Abstract
In order of frequency, the plasma cell lesions affecting the head and neck are multiple myeloma, extramedullary plasmacytoma, plasma cell granuloma, and solitary plasmacytoma of bone. All except plasma cell granuloma are neoplastic and they are interrelated. The solitary plasmacytoma of bone is regarded as a form of multiple myeloma. The extramedullary plasmacytoma may be a lesion of local significance only or may terminate in a disseminated disease, myelomatosis, that differs clinically and prognostically from multiple myeloma.