Overview

Plasmacytoma is a rare cancer that forms in a type of white blood cell called a plasma cell. Healthy plasma cells help the body fight infections by making proteins called antibodies.

In plasmacytoma, cancerous plasma cells grow out of control and form a tumor. The tumor usually forms in a bone. Less often, it forms in soft tissue outside the bones.

Plasmacytoma is related to multiple myeloma, but the two conditions are different. Plasmacytoma usually involves one tumor in one place in the body. Multiple myeloma is more widespread. It affects plasma cells in the bone marrow throughout the body rather than forming just one tumor in one place. Sometimes, plasmacytoma can become multiple myeloma over time.

Plasmacytoma is not the same thing as plasmacytosis. These are two different medical conditions that can be easy to mix up. Plasmacytoma refers to plasma cell cancer. Plasmacytosis means there is an increased number of plasma cells in the blood or bone marrow.

Reactive plasmacytosis happens when the body makes more plasma cells in response to another health condition. This can happen with an infection or an autoimmune disease, which causes the immune system to attack healthy cells and tissues. Reactive plasmacytosis isn't cancer.

Treatment for plasmacytoma may cure it. But sometimes the cancer comes back or changes into multiple myeloma. This change is called progression. Regular follow-up care after plasmacytoma treatment can help find these changes.

Types

There are two main types of plasmacytoma. The type depends on where the tumor starts.

  • Solitary plasmacytoma of bone. This is the more common type. It starts in a bone and may grow into soft tissue nearby. Solitary plasmacytoma of bone most often affects the spine. Other common places where a tumor can form include the pelvis, ribs and skull.
  • Extramedullary plasmacytoma. This type starts in soft tissue outside the bones. It most often starts in the head or neck, such as in the nose, sinuses or throat. It can start in other parts of the body too. Another name for this type is extraosseous plasmacytoma.

A plasmacytoma that starts in a bone may grow into nearby soft tissue. If this happens, it's still a solitary plasmacytoma of bone. It isn't an extramedullary plasmacytoma.

Rarely, an extramedullary plasmacytoma can occur in the skin.

Symptoms

Plasmacytoma symptoms depend on where the tumor is.

Plasmacytoma in a bone often causes pain in the affected area. Other symptoms may include swelling or a lump over or near the affected bone. You also could have a broken bone.

A plasmacytoma in the spine can press on the spinal cord or nearby nerves. This may cause numbness, tingling or weakness in the arms or legs.

Symptoms of extramedullary plasmacytoma depend on where tumors grow. Because these tumors often occur in the head and neck, symptoms may include:

  • A blocked or stuffy nose.
  • Nosebleeds.
  • Trouble swallowing.
  • A hoarse voice.
  • A lump you can see or feel in your head or neck.

Extramedullary plasmacytomas in other parts of the body can cause different symptoms depending on where the tumor grows.

When to seek care

Make an appointment with a doctor or other healthcare professional if you have symptoms that worry you.

When to seek emergency care

Seek emergency medical care if you have plasmacytoma and develop new or worsening:

  • Weakness in your arms or legs.
  • Trouble walking.
  • Numbness, tingling or loss of feeling in your arms or legs.
  • Loss of bladder or bowel function.

These may be signs that a tumor in the spine is pressing on the spinal cord.

Causes

It's not clear what causes plasmacytoma. Researchers have found changes in the genes of plasmacytoma cells. It's not known whether these changes can be passed down in families.

Plasmacytoma happens when a plasma cell turns into a cancer cell. Healthy cells grow and divide based on what the body needs. Old or damaged cells die and are replaced. Cancer cells don't follow these rules. The cells continue living when healthy cells would die. In plasmacytoma, cancer cells multiply out of control and build up in one place, forming a tumor.

Experts don't know why some people with changes in plasma cells develop a single plasmacytoma while others develop multiple myeloma.

Risk factors

There aren't many known risk factors for plasmacytoma. Plasmacytoma is more common in some groups of people. Factors linked with plasmacytoma include:

  • Older age. Plasmacytoma is most often diagnosed in middle-aged and older adults. It's rare before age 40.
  • Sex at birth. Plasmacytoma occurs about twice as often in men as in women.
  • Race. In the United States, plasmacytoma occurs more often in Black people than in white people. It occurs least often in Asian Americans and Pacific Islanders.
  • A weakened immune system. The risk of plasmacytoma is higher in people with weakened immune systems. This is especially true for people who have received organ transplants, such as kidney, liver, heart or lung transplants.

Researchers haven't found evidence that environmental factors increase the risk of plasmacytoma.

Complications

Plasmacytoma can cause complications when a tumor damages a bone or presses on nearby tissues. Possible complications include:

  • Broken bones. A plasmacytoma in a bone can weaken the bone and cause it to break.
  • Pressure on the spinal cord or nerves. A plasmacytoma in the spine can press on the spinal cord or nearby nerves. This can cause weakness, numbness, tingling or trouble walking.
  • Pressure on nearby tissues or organs. An extramedullary plasmacytoma can press on or block nearby structures. The complications depend on where the tumor grows.
By Mayo Clinic Staff