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Diagnosis and tests

How hairy cell leukemia is diagnosed

The related article (“Hairy cell leukemia: symptoms and diagnosis”) explains how to prepare for a bone marrow test. This topic looks at diagnosing hairy cell leukaemia: its particular difficulties and the confirming tests.

Last updated: ~1 min read
An empty syringe and a marrow core.
Figure 1.A dry tap and a biopsy core.

01Short answer

Hairy cell leukaemia is often suspected because of unexplained low blood counts (pancytopenia), very few monocytes and a large spleen. A few “hairy” cells may be seen on a blood smear. Flow cytometry is the key test: along with B-cell markers, the cells show a characteristic combination, positive for CD11c, CD25, CD103 and CD123. A bone marrow aspiration is often “dry” because the marrow is filled with fibrous tissue, so a biopsy is important. The biopsy shows how the cells are spread through the marrow, along with special stains (annexin A1 and others). A molecular test shows the BRAF V600E mutation, present in almost all cases of classic hairy cell leukaemia. This helps distinguish it from a similar “variant” form and from other lymphomas of the spleen.

02Simple explanation

Pancytopenia, few monocytes, a large spleen.

Flow: CD11c, CD25, CD103, CD123.

BRAF V600E: confirmation.

03Scientific explanation

The variant form: hairy cell leukaemia-variant is CD25 negative and usually BRAF V600E negative; its treatment may differ.

Biopsy: reticulin fibres are increased, and aspiration may yield no fluid.

04What happens in the body?

A dry tap and a biopsy

When aspiration yields no fluid, the biopsy gives the diagnosis.

The flow pattern

Four characteristic markers together point to a hairy cell.

A bright group on a screen.
Figure 2.The hairy cell marker pattern.

The BRAF change

BRAF V600E is the genetic signature of the classic form.

DNA with a glowing segment.
Figure 3.The BRAF change — How hairy cell leukemia is diagnosed

05Diagnosing hairy cell leukaemia

Four steps.

Blood — Low counts.1BloodLow counts.
Smear — Hairy cells.2SmearHairy cells.
Biopsy — A marrow sample.3BiopsyA marrow sample.
BRAF — Genetic confirmation.4BRAFGenetic confirmation.

06Tests in diagnosis

TestWhat it shows
Blood countPancytopenia, few monocytes
SmearHairy cells
Flow cytometryCD11c, CD25, CD103, CD123
Bone marrow biopsyInfiltration, fibres
BRAF V600E testThe classic form

07Key terms

Pancytopenia
A fall in all blood cells.
Dry tap
Aspiration that yields no fluid.
BRAF V600E
A mutation common in hairy cell leukaemia.
CD103
A marker found on hairy cells.
Variant form
A similar but different disease.

08Key points

  • Suspicion comes from low counts.
  • Flow cytometry is central.
  • Aspiration may be dry.
  • The biopsy is important.
  • BRAF V600E confirms it.
  • It must be told apart from the variant form.

09Frequently asked questions

Why did the marrow give no fluid?

Because the marrow is fibrous; a biopsy solves this.

What is the BRAF test for?

It confirms the diagnosis and sometimes affects the choice of treatment.

Is this not CLL?

No; the flow pattern and genetics are different (“How CLL is diagnosed”).

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Why did the marrow give no fluid?

  2. What is the BRAF test for?

  3. Is this not CLL?

My questions

12Sources

  1. National Cancer Institute (NCI). Hairy cell leukemia treatment (PDQ), patient version
  2. MedlinePlus. Bone marrow biopsy
  3. National Cancer Institute (NCI). Definition: flow cytometry
  4. National Cancer Institute (NCI). Find an NCI-Designated Cancer Center
  5. Leukaemia Care. Just diagnosed with leukaemia
  6. MedlinePlus (U.S. National Library of Medicine). Talking With Your Doctor
  7. MedlinePlus (U.S. National Library of Medicine). Patient portals — an online tool for your health
  8. American Cancer Society. How Is Childhood Leukemia Classified?
  9. National Cancer Institute (NCI). Cancer Staging
  10. National Cancer Institute (NCI). Performance status — NCI Dictionary of Cancer Terms
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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