Plasma cells are a type of blood cell that helps fight infection. If the plasma cells produced by your bone marrow are abnormal they may cluster together and form a lump of cells either inside a bone or in the soft tissue outside of a bone. This tumour is known as a solitary plasmacytoma (SP).

It’s possible to have several clusters of cells (plasmacytomas) or a single clump (a solitary plasmacytoma). The information in this section is aimed at people with a solitary plasmacytoma.

What is a solitary plasmacytoma (SP)?

There are two different types of solitary plasmacytoma. A solitary bone plasmacytoma (SBP) is a tumour inside a bone. A solitary extramedullary plasmacytoma (SEP) is a tumour in the soft tissue outside of a bone.

Around 250 people find out they have plasmacytomas each year in the UK. It’s not clear exactly what causes them, but we do know that age, sex and environmental factors can affect how likely you are to develop one.

SP symptoms and diagnosis

If your doctor thinks you might have a solitary plasmacytoma, you’ll have some tests to confirm this and rule out the existence of more plasmacytomas or signs of myeloma.

You’ll probably have a biopsy of the area of your body in which your doctor thinks you have a solitary plasmacytoma, a bone marrow biopsy to check the development of new plasma cells, blood tests to check for signs of myeloma, X-rays and scans.

The most common symptom of SP is pain and tenderness around the area of the SP. 

The symptoms you get will depend on what type of plasmacytoma you have. People with SBPs will experience different symptoms to people with SEPs.

SBPs are usually found in long bones like the spine, arms and legs, so you may feel pain and tenderness in these areas.

More than three quarters of SEPs are found in the head and neck, but they are sometimes found in other parts of the body where there’s soft tissue.

If you have been diagnosed with SP and experience any unusual pain, you should go and see your GP so they can check you over.

SP treatment and outlook

Not everyone with a solitary plasmacytoma will have the same outlook, so it’s best to speak to your healthcare team about your individual prognosis. Generally, the outlook for people with a solitary plasmacytoma is good, as it’s usually possible to get rid of the clump of cells with radiotherapy focused on that area (or occasionally surgery to remove the lump).

However, sometimes the plasmacytoma comes back and some patients might develop myeloma – though this is rare for people who have had an SEP. Because of this, if you’ve had a solitary plasmacytoma, you’ll have regular follow-up appointments to check for symptoms of plasmacytomas and myeloma.

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