Plasmacytoma refers to a malignant plasma cell tumor growing within soft tissue or within the skeleton. The skeletal forms usually have other occult tumors and frequently disseminate to multiple myeloma over the course of 5–10 years. The soft tissue forms most often occur in the upper respiratory tract, rarely disseminate, and are cured by resection. Most but not all cases produce paraproteinemia. Solitary tumors in bone can be treated by radiotherapy.