Plasmacytoma

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.

Terminology
There can be some ambiguity when using the word.

"Plasmacytoma" is sometimes equated with "plasma cell dyscrasia" or "solitary myeloma".

It is often used as part of the phrase "solitary plasmacytoma".

It is also used as part of the phrase "extramedullary plasmacytoma ". In this context, "extramedullary" means outside of the bone marrow.

Diagnosis
It is diagnosed by immunoglobulin electrophoresis (or Serum protein electrophoresis) and bone marrow biopsy. Immunoglobulin electrophoresis will show a monoclonal M spike, but bone marrow biopsy will fail to find the classical signs of multiple myeloma. After those two determinations are made, search for the primary site in the soft tissue begins.