What Is Hairy Cell Leukemia?

Medically Reviewed by Carol DerSarkissian, MD on July 26, 2021

Hairy cell leukemia (HCL) is a cancer of the blood that starts in your bone marrow -- the soft tissue inside bones where blood cells are made.

It happens when your bone marrow makes too many white blood cells called B lymphocytes. These cells make this cancer look "hairy" under a microscope, which is where HCL gets its name.

It's a rare condition -- only about 1,000 people get it each year in the U.S. Men get it more often than women, and adults get it more often than children.

HCL is a chronic cancer. That means it doesn't go away completely with treatment. But it grows very slowly. With medical care, you can live a long time with the disease.


Your blood is made of three kinds of cells: red blood cells, platelets, and white blood cells. Each type has a specific job.

  • Red blood cells carry oxygen to your tissues.
  • White blood cells fight infections in your body.
  • Platelets form blood clots to stop bleeding.

All of them are made by your bone marrow. They start out as stem cells. Stem cells are like blank slates. Over time, they can become any of the three types of blood cells.

When you have hairy cell leukemia, a change (or mutation) in your genes causes your body to make too many of the white blood cells called B lymphocytes. As a result, fewer of your blood stem cells grow into other types of white blood cells, platelets, or red blood cells. And the cancerous B lymphocytes aren't normal. They can't fight infection like healthy white blood cells do.

Doctors aren't sure why this mutation happens.


The buildup of these leukemia cells in your blood, bone marrow, spleen, and liver affects how well your blood works in your body. This means you might have symptoms like:

  • Feeling tired and weak
  • Bleeding or bruising
  • Frequent fevers
  • Frequent infections
  • Shortness of breath
  • Weight loss you can't explain

Often, hairy leukemia cells collect in your spleen or liver, which can make them bigger. This can cause pain or a feeling of fullness in your belly just under your ribs.

It's also possible to have no symptoms.

Questions for Your Doctor

If your doctor thinks you might have hairy cell leukemia, it may be helpful to make a list of any questions you have before your next appointment. Some of those might include:

  • Should I do anything before the appointment to prepare?
  • What kinds of tests will I have?
  • Do I need to see a specialist?
  • Do I need treatment?
  • Will I have chemotherapy, immunotherapy, or surgery?
  • What are the side effects from the treatments?
  • Will any of those treatments cure my leukemia?
  • How will this affect my daily life?
  • How will this condition affect my other health conditions?


To get the right diagnosis, you may need to see a hematologist -- a doctor who specializes in blood diseases. They can use several tests to find out if you have HCL:

  • Physical tests. If your spleen is larger than normal because of the hairy cell buildup, your doctor may be able to feel it. They'll press on your belly just below your ribcage. Your doctor may also check you for swollen lymph nodes in your abdomen or in other places on your body.
  • Image tests. Your doctor might order a computerized tomography (CT) scan. Several X-rays are taken from different angles and put together to make a more detailed picture of your spleen.
  • Blood tests. Your doctor will take a sample of your blood and send it to a lab for a complete blood count, or CBC. This will tell if you have unusually low counts of red blood cells, platelets, or certain types of white blood cells. You can also have a test called a peripheral blood smear that looks for hairy leukemia blood cells.
  • Bone marrow biopsy and possibly a bone marrow aspiration. This test looks for signs of cancer in your bone marrow, blood, and bone. Your doctor will put a hollow needle into your breastbone or hipbone and take out a small piece of bone, some bone marrow, and some blood to look at under a microscope. These tests will also help identify mutations that are seen in HCL cells.


The type of treatment your doctor chooses for you will depend on:

  • How many healthy blood cells you have vs. hairy leukemia cells in your blood and bone marrow
  • Whether your spleen is larger than normal
  • Whether you have an infection in your blood or other signs of leukemia (fevers, sweats, weight loss)
  • How many times you've had HCL come back after treatment

Once your doctor has a better idea of how HCL is affecting you, they may recommend one or more of these:

  • If your HCL grows slowly and doesn't cause any symptoms, your doctor might decide you don't need treatment right away and recommend "watchful waiting" before starting a treatment plan.
  • Chemotherapy. This is a combination of powerful drugs that kill cancer cells or make them grow more slowly. There are two options: cladribine (Leustatin) and pentostatin (Nipent). They both are put into your body through an IV. Most people with HCL who take chemotherapy drugs go into complete or partial remission (when there are no signs of cancer in your blood).
  • Immunotherapy. This uses your immune system to fight HCL. Two common therapies that do this are interferon and rituximab (Rituxan). The drug moxetumomab (Lumoxiti) may be used if other treatments haven't helped.
  • Surgery. If your spleen is painful or bursts, you might need to have it removed (a splenectomy). This won't cure your HCL, but your blood count may go back to normal.

What to Expect

Whether you've had treatment for HCL or are just watching it closely, your doctor may ask you to come back every 3 to 6 months for blood tests to see if there have been any changes and to make sure your medical team is managing HCL the right way. These visits are also the time to tell your doctor about anything that's going with you, like new symptoms or side effects from treatment.

Some treatments can cause nausea or skin rashes, and both the treatments and HCL can make you feel tired or weak. Your doctor can help you manage these kinds of things or refer you to another health care professional who can.

HCL can affect other parts of your life, too, like your family finances or your job. Or you might need assistance with child care or housework. Asking questions and getting information about resources early on can help you avoid bigger problems in these areas later. For example, it's a good idea to check into things like insurance, short-term disability benefits, or sick days so you can plan ahead.

Taking Care of Yourself

As you take care of your physical health, don’t forget to take care of the rest of you. Appointments, tests, and treatments can take a toll. Your doctor may suggest massage therapy, yoga, exercise, or other stress-relieving activities.

Good nutrition is an important way to take care of yourself while you heal. Your doctor may recommend a particular diet, or they may suggest sticking to lean protein, whole grains, fruits, and vegetables. Keeping your body as healthy as possible will help fight off infections.

If you need to have your spleen removed, part of your recovery may include physical therapy in the hospital and at home. The goal is to help you move around better and get stronger.

Getting Support

Having family and friends to lean on is great, but sometimes it's good to talk to someone who knows what it’s like to live with a chronic health condition. Ask your doctor’s office for information about support groups for people with hairy cell leukemia.

If a support group isn’t your thing, you may be more comfortable with online discussion boards. Check out the chat sections of the American Cancer Society and the Leukemia & Lymphoma Society websites.

Dealing with a chronic health condition can trigger symptoms of anxiety and depression. A mental health counselor can offer a safe place to share your feelings.

Show Sources


National Cancer Institute: "Hairy Cell Leukemia."

Leukemia & Lymphoma Society: "Hairy Cell Leukemia," "Hairy Cell Leukemia Facts."

Mayo Clinic: "Hairy Cell Leukemia."

Hairy Cell Leukemia Foundation: "About HCL."

American Cancer Society: "Chemotherapy: What it is, How it helps," "Treating Hairy Cell Leukemia."

NYU Langone Health Perlmutter Cancer Center: “Support for Hairy Cell Leukemia.”

Cancer Research UK: "Coping practically."

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