Plasma cell leukemia is an aggressive form of cancer that occurs in the plasma of the bone marrow. It is a rare type of multiple myeloma.

Multiple myeloma is a type of cancer that affects the plasma of the bone marrow. Unlike most forms of myeloma, with multiple myeloma the cancer cells travel outside the bone marrow and into the blood.

A scientist conducting a blood testShare on Pinterest
Cultura RM Exclusive/Jason Butcher/Getty Images

Plasma cell leukemia is a subtype of multiple myeloma. Inside the bones is a substance called marrow. Marrow is spongy and produces stem cells, blood, and some other substances.

Multiple myeloma happens when plasma cells in the bone marrow grow out of control. This can weaken the immune system, the bones, and the organs. It may also cause anemia.

Plasma cell leukemia is a much rarer form of multiple myeloma, affecting one in every million people without a history of myeloma each year. With this type of cancer, the cancerous plasma cells spread to the blood. It is much more aggressive than multiple myeloma, with average survival after diagnosis of about a year.

Stem cell transplants offer hope for prolonged survival, but the overall outlook for people with plasma cell leukemia compared with multiple myeloma still remains poor.

There are two types of plasma cell leukemia. The first is primary plasma cell leukemia, which is cancer that begins in its original form, rather than spreading to the blood from another type of cancer. Primary plasma cell leukemia is genetically distinct from multiple myeloma.

The second type is secondary plasma cell leukemia, which is cancer that happens when multiple myeloma transforms and spreads to the blood. Because modern treatment is prolonging the lives of people with multiple myeloma, secondary plasma cell leukemia is becoming more common.

A small 2006 study of 10 cases found that survival rates for both primary and secondary forms were similar — about 5.9 months after diagnosis. Thanks to stem cell transplants, survival rates may have slightly increased since that time.

Doctors do not know what causes multiple myeloma. The cancer is much more common in Black Americans than white Americans, and slightly more common in men than in women, though researchers do not know why.

Genetic changes in the development of plasma cells may contribute to the development of plasma cell leukemia. But doctors do not know what causes these changes. Because the cancer is so rare, it is difficult to study. Exposure to environmental toxins such as pollution, as well as the cell-damaging effects of age, may play a role.

People with plasma cell leukemia may not have any symptoms. When they do, those symptoms may include:

A doctor may suspect multiple myeloma based on a person’s symptoms. Blood testing may also reveal symptoms of multiple myeloma, such as anemia or high blood calcium.

Some other tests a doctor may use to diagnose plasma cell leukemia as the subtype of multiple myeloma include:

  • Biopsy, to look for cancerous cells in the bone marrow.
  • Laboratory exams of the blood to check for the presence of bone marrow plasma cells.
  • A blood test called an immunoglobulin free light chain.
  • Imaging scans such as CT or MRI to look for cancer-related changes to the bones.

With multiple myeloma, a small number of plasma cells may get into the blood. For a plasma cell leukemia diagnosis, cancerous plasma cells must be in at least 20% of blood cells.

Plasma cell leukemia is a very aggressive cancer. In most cases, doctors cannot cure it. But a type of stem cell transplant called autologous stem cell transplantation has improved survival rates, and in some cases, may send the cancer into remission.

Other treatment options include:

  • Chemotherapy: Chemotherapy kills cancer cells, but it can also kill healthy cells.
  • Steroids: Steroids do not cure the cancer, but they can change how the body responds to the cancer, potentially reducing symptoms or helping prevent some complications.
  • Experimental treatments: Because there are so few treatment options for plasma cell leukemia, doctors may recommend joining a clinical trial.
  • Other drugs: Doctors may use targeted drugs to slow the growth of cancer. In some cases, doctors may prescribe medication to reduce the symptoms of cancer or to combat chemotherapy side effects.

Most people with plasma cell leukemia live for a year or less after diagnosis. But the outlook depends on a person’s overall health, quality of treatment, how early a doctor detects the cancer, and similar factors.

Treatment can prolong the life of people with plasma cell leukemia, and sometimes even eliminate the cancer. A 2020 case report details the case of a 39-year-old Indian man who, after treatment with a range of chemotherapy drugs, the steroid dexamethasone, and a stem cell transplant, had been in remission for 18 months.

Plasma cell leukemia can be a scary diagnosis because of the short life expectancy and aggressive nature of the cancer. While a cure is unlikely, there are treatments that can slow the disease and prolong a person’s life.

Talk with an oncologist about the various options, and ask for a referral to mental health and social support to manage the challenges of living with cancer.