Hairy cell leukemia (HCL) diagnosis

Diagnosing hairy cell leukemia (HCL) usually involves a series of tests. 

HCL is rare and can be confused with other blood diseases, so an accurate diagnosis is essential in order to determine the best treatment options. Therefore, it is important for an experienced doctor to examine the laboratory samples. A doctor who examines lab samples and helps with diagnosis is called a “pathologist”; a pathologist who specializes in blood diseases is called a “hematopathologist.”

Tests your doctor may use to diagnose HCL 

Your doctor may use the following tests to help them diagnose HCL:

Blood tests  

Complete blood count (CBC) with differential: A CBC is a test that measures the number of red blood cells, white blood cells, and platelets in a sample of blood. The “differential” measures the different types of white blood cells in the sample. Usually, people with HCL have low counts of red blood cells, white blood cells, and platelets.  

Peripheral blood smear: In this test, a sample of blood is viewed under a microscope to count different circulating blood cells and to see whether the cells look normal. In patients with HCL, the hematopathologist may observe small- to medium-sized leukemia cells with the presence of hairy-like projections.

Bone marrow tests  

Your doctor or oncologist (cancer specialist) tests your bone marrow. Bone marrow testing involves two steps usually done at the same time in a doctor's office or a hospital: 

• A bone marrow aspiration to remove a liquid marrow sample
• A bone marrow biopsy to remove a small amount of bone filled with marrow

These two tests are used to examine bone marrow cells to find abnormalities and are generally done at the same time. The sample is usually taken from the patient’s hip bone after medicine has been given to numb the skin. For a bone marrow aspiration, a hollow needle is inserted through the hip bone and into the bone marrow to remove a liquid sample of cells. For a bone marrow biopsy, a wider needle is used to remove a small piece of bone that contains marrow. Both samples are examined under a microscope to look for chromosomal and other cell changes. 

Learn more about bone marrow tests. 

View the interactive 3D model to help you visualize and better understand the procedure. Click the "Interact in 3D" button to begin. 

Flow cytometry 

Flow cytometry is a test used to classify cells based on the type of proteins (markers) on the surface of the cells. Hairy cells have a characteristic surface protein pattern that differs from both healthy B cells and other abnormal (malignant) B cells. The pattern of the surface proteins is called the immunophenotype.

Molecular tests 

Molecular tests are very sensitive DNA tests that check for specific genetic mutations in cells. In almost all cases of HCL, the leukemia cells have a mutation of the BRAF V600E gene. The BRAF V600E mutation may serve as a reliable molecular marker to distinguish HCL from other B-cell leukemias and lymphomas.  

Some gene mutations may serve as a factor that will help doctors predict the likely outcome of the disease (a prognosis). Approximately 80 to 90 percent of HCL patients have a hypermutation in immunoglobulin heavy-chain variable gene called IGHV. For example, with conventional chemotherapy, patients who have the IGHV mutation have a better prognosis (meaning a more positive outcome) than those without the mutation, who usually have a poorer prognosis (a less favorable outcome). 

CT or ‘CAT’ scan 

This test creates a series of detailed pictures of areas inside the body taken from different angles. The pictures are made by a computer linked to an X-ray machine. The patient may swallow a dye, or have it injected into a vein, to help the organs or tissues show up more clearly. CT scans of the chest, abdomen, and/or pelvis may be useful under certain circumstances to examine the size of the spleen, liver, and lymph nodes. 

Learn more about the lab and imaging tests doctors use to diagnose HCL.