Plasmacytoma is a localized mass of neoplastic monoclonal plasma cells that represents approximately 5% of all plasma cell neoplasms. There are two separate entities: primary plasmacytoma of the bone and extramedullary plasmacytoma of the soft tissues. Of the extramedullary plasmacytomas, 80% occur in the head and neck, usually in the upper respiratory tract. The median age at diagnosis is 50 years and the male to female ratio is 3:1. Long-term survival is possible following local radiotherapy, particularly for soft tissue presentations. The disease is plasmacytoma (MONDO_0005615).