A plasmacytoma is an abnormal growth of a type of white blood cell called a plasma cell. Plasmacytoma often affects the bone but can also affect other tissues.

Plasmacytoma is rare. For example, plasmacytoma of the bone is the most common type and only makes up about 2 to 5 percent of all malignancies affecting plasma cells.

Keep reading to learn more about plasmacytoma, its symptoms, and how it can be diagnosed and treated.

A plasmacytoma is a cancerous tumor made of abnormal plasma cells. Plasma cells are a type of white blood cell derived from immune cells called B cells. The normal function of plasma cells is to make antibodies to fight infections.

In plasmacytoma, there is only one tumor. This is why you’ll often see it referred to as solitary plasmacytoma.

Over time, it’s possible for plasmacytoma to progress to multiple myeloma. This is a type of cancer where abnormal plasma cells form many tumors in the bone marrow.

There are two main types of plasmacytoma. Let’s look at each one.

Solitary plasmacytoma of bone (SPB)

In SPB, the plasmacytoma comes from plasma cells in the bone marrow. It’s the most common type of plasmacytoma.

SPB can be further divided into two additional subtypes. These are based on whether abnormal plasma cells are also present outside of the plasmacytoma:

  • SPB with no bone marrow involvement. This is when there are no abnormal plasma cells outside of the plasmacytoma.
  • SPB with minimal bone marrow involvement. This is where less than 10 percent of bone marrow cells outside of the plasmacytoma are abnormal plasma cells.

Extramedullary plasmacytoma (EMP)

In EMP, the plasmacytoma develops from plasma cells present outside of the bones. They make up about one-third of all plasmacytomas.

EMPs are most common in the head and neck region, where they can often affect the sinuses and throat. They may also develop in other tissues, such as the lungs and digestive tract.

The symptoms of plasmacytoma can depend on the type of plasmacytoma.

Solitary plasmacytoma of bone (SPB)

The main symptom of SPB is pain in the affected bone. Some examples of the bone types that may be affected by SPB include those of the vertebrae, skull, and thigh bone (femur).

The growth of SPB can also damage the affected bone. This can cause breaks to occur.

Additionally, it’s possible for SPB that affects the skull to cause symptoms like:

Extramedullary plasmacytoma (EMP)

EMPs also mainly cause pain in the affected area. This is because the tumor may press on other nearby tissues as it grows.

It’s also possible for EMPs to cause problems specific to the area where they’ve developed. For example, in addition to pain in the affected area, an EMP in the sinuses may lead to nasal congestion and a reduced sense of smell.

It’s not known what exactly causes plasmacytoma to develop. Some potential risk factors may include:

  • Age. Middle-aged and older people are more likely to develop plasmacytoma. The median age of diagnosis is 55 to 60.
  • Sex. Plasmacytoma is more common in people assigned male at birth.
  • Race. It’s not known why yet, but plasmacytoma has been observed with a greater frequency in African Americans.
  • Environmental exposures. It’s possible that previous exposures to radiation or certain types of chemicals may increase a person’s risk of plasmacytoma.

In addition to taking your medical history and doing a physical exam, a doctor will use the following tests to help make a diagnosis of plasmacytoma:

  • Blood and urine tests. A variety of blood and urine tests can help your doctor determine what’s causing your symptoms. These tests may include:
    • blood and urine immunoglobulin studies, which can detect a protein called M protein (this protein is more commonly seen in multiple myeloma, but may also be found in small amounts in some people with plasmacytoma)
  • Imaging. Imaging can help your doctor see plasmacytoma in the bone or in other tissues. Some of the imaging tests your doctor may order include:
  • Biopsy. Your doctor will take a tissue sample from the tumor to check it for abnormal plasma cells.
  • Bone marrow biopsy. Regardless of whether the tumor is in the bone or not, a bone marrow biopsy is typically done to assess bone marrow health.

Generally speaking, a diagnosis of plasmacytoma can be made if the following are true:

  • A biopsy determines the tumor is made of abnormal plasma cells.
  • Imaging shows the tumor is solitary, meaning no additional tumors are found in the body.
  • A bone marrow biopsy indicates less than 10 percent of the bone marrow is made of abnormal plasma cells.
  • There are no systemic signs of multiple myeloma, such as high calcium levels, anemia, or poor kidney function.

Radiation therapy typically treats plasmacytoma. This type of treatment uses high energy radiation to kill cells in the tumor. The radiation will be directed at the tumor, aiming to spare surrounding tissues from damage.

In rarer cases, surgery to remove the tumor may be an option. The type of procedure that’s used will depend on the tumor’s location.

It’s also possible that radiation therapy may be used after surgery. This helps to kill any remaining tumor cells.

There are several potential complications from plasmacytoma, such as:

  • Fractures. Having SPB can lead to fractures in the bone.
  • Neurological problems. Plasmacytoma may press on nearby nerves, leading to pain or feelings of weakness or numbness, particularly when SPB affects the spine. SPB of the skull can also cause headache and vision problems.
  • POEMS syndrome. POEMS syndrome is extremely rare, but it can happen if your immune system responds abnormally to a tumor. It’s usually associated with SPB and causes five major symptoms:
    • abnormal levels of some hormones
    • production of M proteins by abnormal plasma cells
  • Local complications. EMP can cause complications in the area where it’s located. For example, an EMP in the throat may lead to shortness of breath or trouble speaking or swallowing.

The best way to avoid complications from plasmacytoma is to get treatment. If you develop concerning symptoms, it’s always a good rule of thumb to make an appointment with a doctor to discuss your symptoms.

Progression to multiple myeloma

Plasmacytoma can sometimes progress to multiple myeloma. The risk of this happening can depend on the type of plasmacytoma you have.

For SPB with no bone marrow involvement, the risk of progression to multiple myeloma within 3 years is 10 percent, according to a 2018 research commentary.

SPB with minimal bone marrow involvement has a higher chance of progression. Up to 60 percent of people with this type of plasmacytoma progress to multiple myeloma within 3 years, notes the commentary.

EMP can also turn into multiple myeloma. Research from 2021 estimates this happens in about 15 percent of people.

If treatment is started early and other plasmacytomas aren’t detected later, the outlook for people with plasmacytoma can be quite good.

Between the two types, people with EMP tend to have a better outlook than those with SPB.

A 2017 study included 1,691 people with plasmacytoma. Over a follow-up period of almost 10 years, the median survival time after treatment was 8.12 years. Younger age and treatment with radiation therapy were associated with longer survival after treatment.

Plasmacytoma often responds well to radiation therapy. In fact, radiation therapy can control plasmacytoma in 85 to 90 percent of cases, reports 2018 research. This may include remission or possible cure.

However, it’s still possible for people who have had plasmacytoma to eventually develop multiple myeloma. Additionally, plasmacytoma can sometimes return after treatment.

Because of this, your doctor will continue to monitor your condition, even years after treatment has ended.

Plasmacytoma is a rare type of tumor made of abnormal plasma cells. It can happen either inside or outside the bone.

Radiation therapy can manage plasmacytoma very effectively. It’s still possible for people with plasmacytoma to go on to develop multiple myeloma, but doctors will monitor for this.

If you have symptoms like unexplained pain, particularly in a bone, that doesn’t go away or gets worse, make an appointment with a doctor. They can use a variety of tests to help determine what’s causing your symptoms.