Plasmacytoma (Solitary Plasma Cell Tumor), from the CureRays guide library.

A plasmacytoma is a single tumor made of plasma cells; it is highly sensitive to radiation, which is the main, often curative treatment for this localized disease.

What it is.

A plasmacytoma is a tumor made up of plasma cells — a type of white blood cell that normally makes antibodies to fight infection. Unlike multiple myeloma, which is a cancer of plasma cells spread throughout the bone marrow, a plasmacytoma is a single, localized collection of these cells in one spot. There are two main forms. A solitary plasmacytoma of bone forms within a bone — often a vertebra in the spine, but also the ribs, pelvis, or other bones — and may cause pain, a weakened bone, or a fracture. An extramedullary plasmacytoma forms in soft tissue outside the bone, most often in the head and neck area such as the nasal passages, sinuses, or throat, where it may cause stuffiness, a lump, or local symptoms. Because plasmacytomas share a biology with myeloma, doctors carefully check the bone marrow and blood to confirm the disease is truly limited to one site, and they monitor over time because some plasmacytomas can later progress to multiple myeloma. The encouraging news is that plasma cells are very sensitive to radiation, so a localized plasmacytoma is usually treated — and often cured — with focused radiation therapy. Care is coordinated by a team that typically includes a radiation oncologist and a blood-cancer specialist (hematologist).

How radiation treats it.

Radiation uses focused high-energy beams to damage the DNA inside cancer cells so they can no longer grow and divide. Plasma cells — the cells that make up a plasmacytoma — are among the most radiation-sensitive cancer cells, which is exactly why radiation is the primary treatment and is frequently curative for a localized plasmacytoma. Treatment is delivered as a series of short, painless daily sessions over a few weeks, with the dose carefully shaped to cover the whole tumor while sparing nearby healthy tissue such as the spinal cord, eyes, or organs. For a plasmacytoma in a vertebra, radiation can relieve pain, control the tumor, and help protect the bone. Because some plasmacytomas can later progress to multiple myeloma, your team will continue to monitor your blood and imaging over time even after successful radiation, so that any change can be treated early. Your radiation oncologist will design a plan aimed at eliminating the tumor while protecting the structures around it.

The ways we can treat it.

Targeted external-beam radiation. A precisely shaped beam delivers a curative dose to the single tumor over a series of short daily sessions, taking advantage of how sensitive plasma cells are to radiation.

Intensity-modulated radiation therapy (IMRT). For tumors near sensitive structures — such as the spinal cord, eyes, or head and neck — IMRT shapes the dose to the tumor while sparing nearby healthy tissue.

Stereotactic body radiation therapy (SBRT). In selected cases, highly focused radiation can treat a well-defined tumor, such as one in the spine, with steep dose fall-off to protect the spinal cord.

Questions we hear often.

Is a plasmacytoma the same as multiple myeloma? Not exactly. A plasmacytoma is a single, localized tumor of plasma cells, while multiple myeloma is a cancer of plasma cells spread throughout the bone marrow. They are related, and some plasmacytomas can progress to myeloma over time, which is why your team checks for myeloma at diagnosis and monitors you afterward.

Why is radiation the main treatment? Plasma cells are very sensitive to radiation. Because a plasmacytoma is concentrated in one spot, focused radiation can deliver a curative dose right to the tumor while sparing the rest of the body, making it the primary and often curative treatment for localized disease.

Will it come back or turn into myeloma? Radiation controls the local tumor in most people, and many are cured. However, because there is a chance of later developing multiple myeloma, your care team will keep monitoring your blood, urine, and imaging over time so that, if anything changes, treatment can start early.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.