# Hairy cell leukaemia

Source: https://onco.cc/cancers/hairy-cell-leukemia/  
OnCo record `hairy-cell-leukemia` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Hairy cell leukaemia is a rare, slow B-cell leukaemia with a single defining mutation (BRAF V600E) that is unusually curable: one week of a purine analogue puts most people into remission for years, and BRAF drugs rescue those who relapse.

## Summary

Classic hairy cell leukaemia (HCL) is a mature B-cell neoplasm with a distinctive morphology and immunophenotype (CD11c, CD25, CD103, CD123, annexin A1) and BRAF V600E in essentially all cases (Tiacci 2011); the variant HCL-v lacks BRAF V600E, is CD25-negative, and behaves worse (often MAP2K1-mutant). Patients present with pancytopenia, splenomegaly and infections.

Purine analogues (cladribine or pentostatin) give complete remission in 80-90% with a single course, and adding rituximab (concurrent or delayed) deepens responses and achieves MRD negativity in most (Chihara et al.). Relapse is treated with a second purine analogue course plus rituximab; BRAF inhibition (vemurafenib ± rituximab) gives durable remissions in multiply relapsed disease (Tiacci 2021, NEJM), and BRAF+MEK combinations are an option. Moxetumomab pasudotox (anti-CD22 immunotoxin) was approved in 2018 and withdrawn commercially in 2023. Ibrutinib has modest activity. Overall survival is now close to age-matched controls.

## Fields

- Kind: Cancer
- Last checked: 2026-09-08
- Tags: gap-fill; haematologic
- Group: haematologic
- Burden: Hairy cell leukaemia causes about 1,000-1,200 cases per year in the US (~2% of leukaemias); median age ~55, 4:1 male.
- Subtypes: Classic HCL (BRAF V600E); HCL variant (BRAF-wild-type, CD25-negative, MAP2K1 mutations); IGHV4-34 HCL (poor risk)
- Biomarkers: BRAF V600E (IHC VE1, PCR, ddPCR); Flow cytometry: CD11c, CD25, CD103, CD123; MRD by flow or BRAF ddPCR; IGHV4-34 usage; MAP2K1 mutations (variant)

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/hairy-cell-leukemia/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/hairy-cell-leukemia/#overview [3 state-of-the-art points]
- What it is (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/hairy-cell-leukemia/#what-it-is [3 subtypes]
- Finding it (on the hub): How it shows itself, how it is confirmed, what screening exists, and the biomarkers clinicians test for. https://onco.cc/cancers/hairy-cell-leukemia/#finding-it [5 biomarkers]
- Treating it (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/hairy-cell-leukemia/#treating-it [3 settings, 3 decisions with options]
- Evidence (on the hub): Trials recruiting now, the landmark trials, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/hairy-cell-leukemia/#evidence [1 trial, 1 key paper, 7 milestones]
- The science (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/hairy-cell-leukemia/#science [7 targets, 1 pathway]
- Where you are (own page): Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record. https://onco.cc/cancers/hairy-cell-leukemia/where-you-are/
- Living with it (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/hairy-cell-leukemia/#living-with-it [15 questions, 6 red cards]
- What is coming (own page): Everything in development, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/hairy-cell-leukemia/coming/ [8 medicines, 1 trial, 3 open problems]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/hairy-cell-leukemia/data/ [36 connected records]

## Standard of care

- First line, symptomatic: Cladribine (5-7 days) or pentostatin, with rituximab concurrent or delayed (improves MRD-negative CR). ([Cladribine](https://onco.cc/drugs/cladribine/), [Rituximab](https://onco.cc/drugs/rituximab/))
- Relapse after >2 years: Repeat purine analogue + rituximab. ([Cladribine](https://onco.cc/drugs/cladribine/), [Rituximab](https://onco.cc/drugs/rituximab/))
- Early relapse or refractory: Vemurafenib + rituximab (or dabrafenib-trametinib); ibrutinib; clinical trial. Moxetumomab pasudotox produced durable remissions but was withdrawn from sale in 2023 and is no longer available. ([Vemurafenib](https://onco.cc/drugs/vemurafenib/), [Rituximab](https://onco.cc/drugs/rituximab/), [Dabrafenib + trametinib](https://onco.cc/drugs/dabrafenib-trametinib/), [Ibrutinib](https://onco.cc/drugs/ibrutinib/), [Moxetumomab pasudotox](https://onco.cc/drugs/moxetumomab-pasudotox/))

## State of the art

- One week of cladribine remains one of the most effective single treatments in oncology.
- BRAF V600E is universal in classic HCL; vemurafenib-rituximab produces MRD-negative remissions in most relapsed patients without chemotherapy.
- Life expectancy is near normal; the residual problems are infection during induction and the aggressive variant.

## Open problems

- Variant HCL and IGHV4-34 disease respond poorly to purine analogues.
- Infection risk during induction neutropenia.
- Whether MRD eradication should be a treatment goal.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Hairy_cell_leukemia
- NCCN Guidelines: Hairy Cell Leukemia: https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1481
- Hairy Cell Leukemia Foundation: https://www.hairycellleukemia.org/
- Tiacci 2011 NEJM: https://doi.org/10.1056/NEJMoa1014209

## Connected records

- cancers: [Chronic lymphocytic leukaemia](https://onco.cc/cancers/cll/), [Chronic myeloid leukaemia (CML)](https://onco.cc/cancers/cml/), [Leukaemia (all types)](https://onco.cc/cancers/leukaemia/), [Splenic B-cell lymphoma/leukaemia with prominent nucleoli (formerly B-cell prolymphocytic leukaemia and hairy cell leukaemia variant)](https://onco.cc/cancers/splenic-b-cell-lymphoma-leukaemia-prominent-nucleoli/), [Splenic marginal zone lymphoma](https://onco.cc/cancers/splenic-marginal-zone-lymphoma/)
- technologies: [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/), [Monoclonal antibodies](https://onco.cc/technologies/monoclonal-antibody/), [Multiparameter flow cytometry MRD](https://onco.cc/technologies/flow-cytometry-mrd/), [Small-molecule kinase inhibitors](https://onco.cc/technologies/kinase-inhibitors/)
- targets: [Adenosine deaminase (ADA)](https://onco.cc/targets/ada/), [BRAF](https://onco.cc/targets/braf/), [BTK (Bruton tyrosine kinase)](https://onco.cc/targets/btk/), [CD123](https://onco.cc/targets/cd123/), [CD20](https://onco.cc/targets/cd20/), [CD22](https://onco.cc/targets/cd22/), [Interferon alpha receptor (IFNAR1)](https://onco.cc/targets/ifnar1/)
- drugs: [Cladribine](https://onco.cc/drugs/cladribine/), [Dabrafenib + trametinib](https://onco.cc/drugs/dabrafenib-trametinib/), [Ibrutinib](https://onco.cc/drugs/ibrutinib/), [Interferon alfa-2a/2b](https://onco.cc/drugs/interferon-alfa/), [Moxetumomab pasudotox](https://onco.cc/drugs/moxetumomab-pasudotox/), [Pentostatin](https://onco.cc/drugs/pentostatin/), [Rituximab](https://onco.cc/drugs/rituximab/), [Vemurafenib](https://onco.cc/drugs/vemurafenib/)
- companies: [AstraZeneca](https://onco.cc/companies/astrazeneca/), [Roche / Genentech](https://onco.cc/companies/roche-genentech/)
- pathways: [RAS / RAF / MEK / ERK (MAPK)](https://onco.cc/pathways/ras-mapk/)
- terms: [Minimal / molecular residual disease (MRD)](https://onco.cc/terms/mrd/)
- key papers: [BRAF mutations in hairy-cell leukemia](https://onco.cc/key-papers/paper-tiacci-n-engl-j-med/)
- people: [Sascha Dietrich](https://onco.cc/people/sascha-dietrich/)
- trials: [Randomized Phase II Trial of Rituximab With Either Pentostatin or Bendamustine for Multiply Relapsed or Refractory Hairy Cell Leukemia](https://onco.cc/trials/nct01059786/)

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JSON: https://onco.cc/api/v1/entities/hairy-cell-leukemia.json