Hairy Cell Leukemia
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Leukemia is a condition where the bone marrow makes too many immature white blood cells. In Hairy Cell Leukemia (HCL) is a specific kind of leukemia affecting B­-lymphocytes, a type of white blood cell. In HCL fine, hair-like strands develop around the outside of abnormal B­-lymphocytes, visible under a microscope. HCL accounts for about 2% of all cases of leukemia, it is a chronic leukemia (tending to develop slowly) and occurs most frequently in people aged 40-60.

(UK spelling: Leukaemia)

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Latest Research Publications
Molecular Genetics of Hairy Cell Leukemia
Chronic Lymphocytic Leukemia - CLL

Information Patients and the Public (10 links)


Information for Health Professionals / Researchers (4 links)

Latest Research Publications

This list of publications is regularly updated (Source: PubMed).

Morgan EA, Yu H, Pinkus JL, Pinkus GS
Immunohistochemical detection of hairy cell leukemia in paraffin sections using a highly effective CD103 rabbit monoclonal antibody.
Am J Clin Pathol. 2013; 139(2):220-30 [PubMed]
Detection of the integrin subunit CD103 is a useful diagnostic tool in the diagnosis of hairy cell leukemia (HCL). Currently, flow cytometric analysis (FC) and frozen section immunohistochemistry (IHC) represent the only available methods of detection. This study is the first to describe the successful use of a CD103 antibody to identify HCL and HCL-variant in paraffin sections of formalin- or Bouin solution- fixed specimens (n = 68) using an immunoperoxidase technique. In other B-cell lymphoproliferative disorders that morphologically may resemble HCL, including chronic lymphocytic leukemia/small lymphocytic lymphoma (n = 32), mantle cell lymphoma (n = 23), lymphoplasmacytic lymphoma (n = 27), follicular lymphoma (n = 7), and marginal zone lymphoma (n = 13), lymphoid cells are nonreactive for CD103. In HCL, the CD103 staining pattern is predominantly membranous with delineation of delicate cytoplasmic projections. This CD103 antibody is an extremely valuable addition to the IHC panel for the diagnosis of HCL, especially in cases lacking FC analysis.


Shao H, Calvo KR, Grönborg M, et al.
Distinguishing hairy cell leukemia variant from hairy cell leukemia: development and validation of diagnostic criteria.
Leuk Res. 2013; 37(4):401-9 [PubMed]
Hairy cell leukemia (HCL) and hairy cell leukemia-variant (HCL-v) are rare diseases with overlapping clinico-pathological features. We performed flow cytometry analysis (FCM) of 213 cases (169 HCL, 35 HCL-v, 9 splenic marginal zone lymphoma (SMZL)), correlating results with available corresponding clinical and morphological data. FCM distinguished HCL-v from HCL and SMZL based solely upon expression of four antigens (CD11c, CD25, CD103, CD123) combined with B-cell markers (CD19, CD20, CD22). HCL-v expressed bright CD20, bright CD22, CD11c(100%), CD103(100%), dim(40%) or negative(60%) CD123, and uniformly lacked CD25(100%). HCL expressed bright CD20, bright CD22, bright CD11c, bright CD25, CD103, and bright homogeneous CD123(100%). Aberrant expression of CD5(2%/3%), CD10(12%/3%), CD23(21%/11%), CD38(14%/0%), CD2(2%/9%), CD4(0.5%/0%) and CD13(0.5%/3%), was observed in HCL/HCL-v, respectively. SMZL cases were CD103(-) and CD123(-) except for one case with dim CD123. HCL showed significantly greater marrow infiltration over HCL-v. Prominent nucleoli were observed in most HCL-v but rarely in HCL. A third of HCL and HCL-v marrows were hypocellular or aplastic-appearing. Detection of BRAFV600E mutation and annexin A1 were examined in a subset of cases to further validate FCM diagnostic criteria. HCL-v was negative for both annexin A1 (100%) and BRAFV600E mutation (100%), in contrast to HCL (74% positive for annexin A1; 76% positive for BRAFV600E mutation). HCL-v is resistant to traditional HCL therapy, making accurate diagnosis imperative. We have defined FCM criteria for differentiation of HCL-v from HCL and SMZL.


Warden DW, Ondrejka S, Lin J, et al.
Phospho-ERK(THR202/Tyr214) is overexpressed in hairy cell leukemia and is a useful diagnostic marker in bone marrow trephine sections.
Am J Surg Pathol. 2013; 37(2):305-8 [PubMed]
BRAF V600E mutations are present in virtually all cases of hairy cell leukemia (HCL). We hypothesized that detection of phospho-ERK (pERK) in tissue sections may be a useful marker for diagnosis of HCL. pERK/CD20 double immunostaining was performed on 90 formalin-fixed bone marrow trephine samples affected with small B-cell lymphoproliferative disorders, including 28 cases of HCL. pERK staining was observed in all 28 cases of HCL and in 1 of 62 cases of non-HCL B-cell lymphoproliferative disorders. By allele-specific polymerase chain reaction, all 11 cases of HCL with available DNA were positive for BRAF V600E, as was the 1 pERK non-HCL case. The remaining 31 non-HCL cases tested were negative for BRAF V600E. The sensitivity and specificity of pERK for diagnosis of HCL was 100% and 98%, respectively. We conclude that the presence of pERK as detected by immunohistochemical staining is a useful surrogate marker for BRAF V600E in the diagnosis of HCL.


Laurini JA, Aoun P, Iqbal J, et al.
Investigation of the BRAF V600E mutation by pyrosequencing in lymphoproliferative disorders.
Am J Clin Pathol. 2012; 138(6):877-83 [PubMed]
The presence of the BRAF c.1799T>A V600E mutation was recently described in cases of hairy cell leukemia (HCL) but not in other common lymphomas. However, many uncommon subtypes of lymphoma have not been studied. We designed a BRAF pyrosequencing assay specific for the V600E mutation, which has a sensitivity of 5% and is applicable to paraffin-embedded tissue. DNA was sequenced in 9 cases of HCL; 6 cases of variant HCL; 10 cases each of nodal marginal zone lymphoma (NMZL), extranodal marginal zone lymphoma (ENMZL), posttransplantation lymphoproliferative disorder (PTLD), and large granular lymphocyte (LGL) proliferations; 11 cases of peripheral T-cell lymphoma (PTCL); and 12 cases of anaplastic large cell lymphoma (ALCL). All (100%) cases of HCL were positive for BRAF mutations. No mutations were identified in variant HCL, NMZL, ENMZL, PTLD, PTCL, ALCL, or LGL proliferations. Among lymphoproliferative disorders, BRAF mutations are restricted to HCL.


Subhawong AP, Subhawong TK, Ali SZ
Hairy cell leukemia presenting as a peripancreatic mass: cytomorphology and radiographic correlates.
Acta Cytol. 2012; 56(4):463-6 [PubMed]
Hairy cell leukemia (HCL) usually presents with peripheral cytopenias, diffuse marrow infiltration, and splenomegaly. This chronic lymphoproliferative disorder is not typically associated with lymphadenopathy or mass lesions. We report a case of HCL first treated by splenectomy, followed by several years of interferon therapy. Twenty-five years later, the patient presented with weight loss, fatigue, and a large PET-avid mass surrounding the head of the pancreas. Fine-needle aspiration was pursued to investigate the unusual and infiltrative appearance of the lesion, which was suggestive of another primary malignancy. Cytology smears showed discohesive lymphoid cells with round nuclei and delicate cytoplasmic projections. Flow cytometry confirmed the presence of a clonal B-cell population with bright expression of CD20 as well as CD25 and CD103, diagnostic of HCL. This is the first report of HCL presenting as a peripancreatic mass. The importance of correlation with radiology and clinical history is emphasized when evaluating such lesions.


Verma S, Greaves WO, Ravandi F, et al.
Rapid detection and quantitation of BRAF mutations in hairy cell leukemia using a sensitive pyrosequencing assay.
Am J Clin Pathol. 2012; 138(1):153-6 [PubMed]
BRAF protooncogene is an important mediator of cell proliferation and survival signals. BRAF p.V600E mutation was recently described as a molecular marker of hairy cell leukemia (HCL). We developed and validated a pyrosequencing-based approach that covers BRAF mutational hotspots in exons 11 (codon 468) and 15 (codons 595 to 600). The assay detects BRAF mutations at an analytical sensitivity of 5%. We screened 16 unenriched archived bone marrow aspirate samples from patients with a diagnosis of HCL (n = 12) and hairy cell leukemia-variant (HCL-v) (n = 4) using pyrosequencing. BRAF p.V600E mutation was present in all HCL cases and absent in all HCL-v. Our data support the recent finding that BRAF p.V600E mutation is universally present in HCL. Moreover, our pyrosequencing-based assay provides a convenient, rapid, sensitive, and quantitative tool for the detection of BRAF p.V600E mutations in HCL for clinical diagnostic testing.


Girardi K, Paviglianiti A, Cirillo M, et al.
Tuberculous meningoencephalitis in a patient with hairy cell leukemia in complete remission.
J Clin Exp Hematop. 2012; 52(1):31-4 [PubMed]
Tuberculous meningoencephalitis is a rare disease associated with high morbidity and mortality. We report a patient with hairy cell leukemia in complete remission who, after a single cycle of chemotherapy with cladribine, presented fever and neurological deficits. Laboratory diagnosis of tuberculous meningoencephalitis was made by polymerase chain reaction testing for Mycobacterium tuberculosis in cerebrospinal fluid. Despite the prompt institution of antitubercular-therapy, patient's general condition did not improve and he died. Mycobacterial infection should be considered in patients with intra-cranial lesions, affected by hematological malignancies and persistent immunosuppression.


Ruiz-Delgado GJ, Tarín-Arzaga LC, Alarcón-Urdaneta C, et al.
Treatment of hairy cell leukemia: long-term results in a developing country.
Hematology. 2012; 17(3):140-3 [PubMed]
Twenty-nine consecutive patients with hairy cell leukemia (HCL) were treated in two institutions with interferon (IFN, n = 18) or cladribine (n = 11), between July 1987 and May 2011. Median age was 62 (range 29-83) years; there were 21 males and 8 females. Seven of the 18 patients in the IFN group (39%) achieved a complete remission (CR), whereas all the patients in the 2-CDA group entered a CR. Three patients in the 2-CDA group relapsed and needed an additional course of the drug, 2, 3 and 6 years after the initial one. The median overall survival (OS) of the whole group has not been reached, being above 217 months, the 217-month OS being 91%. The survival of patients treated with either IFN or 2-CDA was not statistically different (94% OS at 217 months versus 91% OS at 133 months, respectively). The data that we present here suggest that treatment of HCL with either 2-CDA or IFN is equally effective; treatment costs with IFN are substantially lower than those of the purine analog.


Furmanczyk PS, Lisle AE, Caldwell RB, et al.
Langerhans cell sarcoma in a patient with hairy cell leukemia: common clonal origin indicated by identical immunoglobulin gene rearrangements.
J Cutan Pathol. 2012; 39(6):644-50 [PubMed]
Histiocytic/dendritic cell sarcomas are rare tumors, a few of which have been reported in association with B-cell lymphoma/leukemia. Isolated reports have documented identical immunoglobulin gene rearrangements suggesting a common clonal origin for both the sarcoma and the B-cell neoplasm from individual patients. We report a case of a 75-year-old male with hairy cell leukemia who subsequently developed Langerhans cell sarcoma 1 year after his primary diagnosis of leukemia. The bone marrow biopsy containing hairy cell leukemia and skin biopsies of Langerhans cell sarcoma were evaluated by routine histology, immunohistochemistry, flow cytometric immunophenotyping and PCR-based gene rearrangement studies of the immunoglobulin heavy chain and kappa genes. The hairy cell leukemia showed characteristic morphologic, immunohistochemical and flow cytometric features. The Langerhans cell sarcoma showed pleomorphic cytology, a high mitotic rate and characteristic immunohistochemical staining for Langerin, S100 and CD1a. There was no evidence of B-cell differentiation or a background B-cell infiltrate based on the absence of immunoreactivity with antibodies to multiple B-cell markers. Identical immunoglobulin gene rearrangements were identified in both the hairy cell leukemia and Langerhans cell sarcoma specimens. Despite the phenotypic dissimilarity of the two neoplasms, identical immunoglobulin gene rearrangements indicate a common origin.


Hockley SL, Else M, Morilla A, et al.
The prognostic impact of clinical and molecular features in hairy cell leukaemia variant and splenic marginal zone lymphoma.
Br J Haematol. 2012; 158(3):347-54 [PubMed]
Hairy cell leukaemia variant (HCL-variant) and splenic marginal zone lymphoma (SMZL) are disorders with overlapping features. We investigated the prognostic impact in these disorders of clinical and molecular features including IGH VDJ rearrangements, IGHV gene usage and TP 53 mutations. Clinical and laboratory data were collected before therapy from 35 HCL-variant and 68 SMZL cases. End-points were the need for treatment and overall survival. 97% of HCL-variant and 77% of SMZL cases required treatment (P = 0·009). Survival at 5 years was significantly worse in HCL-variant [57% (95% confidence interval 38-73%)] compared with SMZL [84% (71-91%); Hazard Ratio 2·25 (1·20-4·25), P = 0·01]. In HCL-variant, adverse prognostic factors for survival were older age (P = 0·04), anaemia (P = 0·01) and TP 53 mutations (P = 0·02). In SMZL, splenomegaly, anaemia and IGHV genes with >98% homology to the germline predicted the need for treatment; older age, anaemia and IGHV unmutated genes (100% homology) predicted shorter survival. IGHV gene usage had no impact on clinical outcome in either disease. The combination of unfavourable factors allowed patients to be stratified into risk groups with significant differences in survival. Although HCL-variant and SMZL share some features, they have different outcomes, influenced by clinical and biological factors.


Andrulis M, Penzel R, Weichert W, et al.
Application of a BRAF V600E mutation-specific antibody for the diagnosis of hairy cell leukemia.
Am J Surg Pathol. 2012; 36(12):1796-800 [PubMed]
In recent times BRAF V600E mutations have emerged as a genetic hallmark of hairy cell leukemia (HCL). This specific point mutation is present in virtually all cases of HCL but is exceedingly rare in other peripheral B-cell neoplasms. In this study we investigated the application of a BRAF V600E mutation-specific antibody (clone VE1) to differentiate HCL from HCL mimics, such as HCL variant and splenic marginal zone lymphoma. A total of 52 routinely processed formalin-fixed paraffin-embedded tissue specimens were investigated (bone marrow, n=46; spleen, n=6) for expression of V600E-mutated BRAF protein. All 32 cases of HCL were scored positive, and all non-HCL cases were scored negative. In 28 of 30 HCL cases the presence of a BRAF V600E mutation could be confirmed by direct sequencing, whereas no BRAF mutations were detected among 20 HCL mimics. We further screened 228 mature B-cell neoplasms with VE1 and detected 1 positive case of chronic lymphocytic leukemia. Sequencing confirmed the presence of a BRAF V600E mutation. In conclusion, we demonstrate that VE1 immunohistochemistry can be used to reliably differentiate HCL from HCL-mimicking entities. This on-slide technique might be particularly helpful in interpreting challenging biopsies with low tumor content.


Galani KS, Subramanian PG, Gadage VS, et al.
Clinico-pathological profile of Hairy cell leukemia: critical insights gained at a tertiary care cancer hospital.
Indian J Pathol Microbiol. 2012 Jan-Mar; 55(1):61-5 [PubMed]
CONTEXT: Hairy cell leukemia (HCL) is a rare, low grade, B-cell neoplasm with a characteristic morphologic and immunophenotypic profile. It has to be distinguished from chronic lymphoproliferative disorders because of different treatment protocol and clinical course.
AIMS: To evaluate clinicopathological features including immunophenotypic analysis of cases diagnosed as HCL.
MATERIALS AND METHODS: The present study included 28 cases diagnosed over a period of nine years (2002-2010). Clinical presentation, complete blood count, bone marrow aspirate, and flow cytometric analysis of cases were reviewed. Treatment and follow-up details (ranging from 3-90 months) were noted.
RESULTS: This study revealed 28 cases (referrals-7, indoor-21), aged 26-69 years with a median age of 47 years, with a male predominance (M:F=6:1). The presenting complaints were weakness (80%) followed by fever (56%) and abdominal pain. Physical examination revealed splenomegaly in most patients (92%) and hepatomegaly in a minority (28%). The common laboratory features were anemia in 23 cases, pancytopenia in 14 cases, while two patients had leukocytosis and three patients had normal WBC count. Dry tap was observed in 84% of the cases where hairy cells constituted 16-97% of non-erythroid nucleated cells. Tartarte resistant acid phosphate staining was positive in all the eight cases where it was done. CD5 was negative in all the cases, while CD10 was expressed in three cases (13%) and CD23 in five cases (19%).
CONCLUSIONS: Though pancytopenia is common, occasional patient can present with normal blood counts or leukocytosis. Few unusual findings include presence of lymphadenopathy, absence of palpable splenomegaly, and expression of CD23 and CD10 by the leukemic cells.


Kreitman RJ, Tallman MS, Robak T, et al.
Phase I trial of anti-CD22 recombinant immunotoxin moxetumomab pasudotox (CAT-8015 or HA22) in patients with hairy cell leukemia.
J Clin Oncol. 2012; 30(15):1822-8 [PubMed] Free Access to Full Article
PURPOSE: To conduct a phase I dose-escalation trial assessing safety and response of recombinant immunotoxin moxetumomab pasudotox (CAT-8015, HA22) in chemotherapy-resistant hairy cell leukemia (HCL).
PATIENTS AND METHODS: Eligible patients had relapsed/refractory HCL after ≥ two prior therapies and required treatment because of abnormal blood counts. Patients received moxetumomab pasudotox 5 to 50 μg/kg every other day for three doses (QOD ×3), with up to 16 cycles repeating at ≥ 4-week intervals if patients did not experience disease progression or develop neutralizing antibodies.
RESULTS: Twenty-eight patients were enrolled, including three patients each at 5, 10, 20, and 30 μg/kg, four patients at 40 μg/kg, and 12 patients at 50 μg/kg QOD ×3 for one to 16 cycles each (median, four cycles). Dose-limiting toxicity was not observed. Two patients had transient laboratory abnormalities consistent with grade 2 hemolytic uremic syndrome with peak creatinine of 1.53 to 1.66 mg/dL and platelet nadir of 106,000 to 120,000/μL. Drug-related toxicities in 25% to 64% of the 28 patients included (in decreasing frequency) grade 1 to 2 hypoalbuminemia, aminotransferase elevations, edema, headache, hypotension, nausea, and fatigue. Of 26 patients evaluable for immunogenicity, 10 patients (38%) made antibodies neutralizing more than 75% of the cytotoxicity of 1,000 ng/mL of immunotoxin, but this immunogenicity was rare (5%) after cycle 1. The overall response rate was 86%, with responses observed at all dose levels, and 13 patients (46%) achieved complete remission (CR). Only 1 CR lasted less than 1 year, with the median disease-free survival time not yet reached at 26 months.
CONCLUSION: Moxetumomab pasudotox at doses up to 50 μg/kg QOD ×3 has activity in relapsed/refractory HCL and has a safety profile that supports further clinical development for treatment of this disease.


Fino P, Fioramonti P, Onesti MG, et al.
Skin metastasis in patient with hairy cell leukemia: case report and review of literature.
In Vivo. 2012 Mar-Apr; 26(2):311-4 [PubMed]
The reported case of Hairy cell leukemia (HCL) refers to a 47-year-old man with pancytopenia, splenomegaly, a month and a half history of dyspnea on mild effort and in common daily activities and a purplish-brown cutaneous node on the back of the left hand at the time of hospital admission. Bone marrow aspiration showed an infiltration by a lymphoproliferative malignancy and the following cytochemical studies on bone marrow sample led to diagnosis of HCL. The biopsy of the skin lesion revealed a infiltrate of medium and large-size cells in the dermis with the the same cytologic features of leukemic blasts appearing in the bone marrow, upon which the diagnosis of Leukemia cutis was established. The differential diagnosis of leukemia includes other neoplastic hematopoietic disorders, such as lymphoma, myelodysplastic syndromes, multiple myeloma, aplastic anemia, severe megaloblastic anemia, severe lymphocytosis, severe monocytosis, and bone marrow failure. In our case, the skin lesion was surgically removed and then left to heal by secondary intention due to the presence of bacterial infection by Staphylococcus aureus and Streptococcus pyogenes. The wound was finally medicated to total healing with Promogran®, an advanced dressings which consists of a sterile, freeze-dried matrix composed of collagen and oxidised regenerated cellulose. The importance of our case lies in the fact that cases with association of HCL with leukemia cutis are very rare, and furthermore that after the excision of the skin lesion of the left hand, the surgeons heal to let the wound close by secondary intention.


Schnittger S, Bacher U, Haferlach T, et al.
Development and validation of a real-time quantification assay to detect and monitor BRAFV600E mutations in hairy cell leukemia.
Blood. 2012; 119(13):3151-4 [PubMed]
The BRAFV600E mutation was recently detected in hairy cell leukemia (HCL) by whole exome sequencing. To make use of this new marker for diagnosis and follow-up of HCL, we developed a BRAFV600Emut-specific quantitative real-time PCR assay and validated it in 117 HCL patients and 102 non-HCL/BRAFwt patients. The cut-off level to discriminate BRAFV600E-positive/-negative cases was set at 0.023% BRAFV600E/BRAFwt. A total of 115 of 117 HCL (98.3%) demonstrated percentage BRAFV600E/BRAFwt above the cut-off (mean, 29.6 ± 41.1). The remaining 2 of 117 HCL with lower percentage BRAFV600E/BRAFwt ratios were also BRAFwt by deep-sequencing technology. Sixteen HCL-variant patients showed percentage BRAFV600E/BRAFwt values corresponding to "non-HCL." Follow-up studies in 19 HCL cases demonstrated a decrease of percentage BRAFV600E/BRAFwt during therapy. The log-reductions as determined by RT-PCR and immunophenotyping correlated significantly (P < .001). In conclusion, we confirmed BRAFmut as a useful marker in HCL, its absence in HCL variant, and developed an RT-PCR-based assay to monitor minimal residual disease in HCL.


Langabeer SE, O'Brien D, Liptrot S, et al.
Correlation of the BRAF V600E mutation in hairy cell leukaemia with morphology, cytochemistry and immunophenotype.
Int J Lab Hematol. 2012; 34(4):417-21 [PubMed]
Hairy cell leukaemia (HCL) has distinct clinical, morphological and immunophenotypic features with no recurrent cytogenetic or molecular abnormalities reported until the recent description of the BRAF V600E mutation in patients with classical HCL. The incidence of this mutation was sought in 27 patients with either classical HCL or HCL variant by an allele-specific PCR approach and findings related to morphology, cytochemistry and immunophenotype. A high degree of correlation was noted between the presence of BRAF V600E and established diagnostic criteria in 26/27 patients with HCL/HCL variant. Detection of the BRAF V600E mutation is therefore a useful adjunct in the differential diagnosis of HCL and HCL variant and highlights the value of a multifaceted approach to the diagnosis of this malignancy.


Ewalt M, Nandula S, Phillips A, et al.
Real-time PCR-based analysis of BRAF V600E mutation in low and intermediate grade lymphomas confirms frequent occurrence in hairy cell leukaemia.
Hematol Oncol. 2012; 30(4):190-3 [PubMed]
Hairy cell leukaemia (HCL) is a rare type of B-cell non-Hodgkin lymphoma (B-NHL), which is not known to be associated with any characteristic recurrent karyotypic abnormality. A recent study that used massively parallel whole exome sequencing identified an activating V600E mutation in BRAF, which appeared specific for HCL. Here, we confirm the specificity of BRAF V600E for HCL among low and intermediate grade B-NHL and describe a real-time polymerase chain reaction method for detecting this mutation in cases with low tumour burden. The V600E mutation does not appear to be associated with microsatellite instability, unlike the case in colorectal cancer. Thus, in conjunction with prior data, our results suggest incorporation of BRAF V600E mutation analysis in the diagnostic workup of HCL cases. Additionally, targeting the Ras-Raf-Mek-Erk-Map kinase pathway should be investigated as a potential therapeutic strategy for patients with this disease.


Gerrie AS, Zypchen LN, Connors JM
Fludarabine and rituximab for relapsed or refractory hairy cell leukemia.
Blood. 2012; 119(9):1988-91 [PubMed]
The purine analogs, pentostatin and cladribine, induce high remission rates when used as first-line monotherapy for hairy cell leukemia (HCL); however, patients continue to relapse. Re-treatment with the same or alternate purine analog produces lower response rates and a shorter duration of response. Fludarabine is another purine analog widely used in indolent lymphoid cancers, often in combination with rituximab, but there are few reports of its use in HCL. We identified 15 patients treated in British Columbia with fludarabine and rituximab (FR) from 2004 to 2010 for relapsed/refractory HCL after first-line cladribine (n = 3) or after multiple lines of therapy (n = 12). All patients with available response data responded to FR. With median follow-up of 35 months, 14 patients remain progression-free, whereas 1 patient has developed progressive leukemia and died. Five-year progression-free and overall survivals are 89% and 83%, respectively. FR is a safe and effective therapeutic option for relapsed/refractory HCL.


Naik RR, Saven A
My treatment approach to hairy cell leukemia.
Mayo Clin Proc. 2012; 87(1):67-76 [PubMed] Free Access to Full Article
Hairy cell leukemia (HCL) is a rare chronic lymphoproliferative disorder characterized by circulating B cells with cytoplasmic projections, pancytopenia, splenomegaly, and a typical flow cytometry pattern. Recently, the BRAF V600E mutation was uniformly identified in one HCL series, which may provide insights into the pathogenic mechanisms. The disease course is usually indolent but inexorably progressive. Patients require treatment when they have significant cytopenia or occasionally recurrent infections from immunocompromise. In the mid-1980s, interferon replaced splenectomy as the initial treatment. A few years later, 2 purine nucleoside analogs, cladribine and pentostatin, showed promising activity in HCL. Complete response rates approached 95% with cladribine given as a single 7-day intravenous infusion. Newer methods of cladribine administration and modified dosing schedules have since been studied. Pentostatin response rates are comparable. We generally prefer cladribine because of its ease of administration, single infusion schema, and favorable toxicity profile. Since the introduction of these drugs, which have never been randomly compared, long-term follow-up studies have confirmed impressive and durable response durations. However, roughly 40% of patients with HCL eventually relapse. In this setting, patients can be re-treated with purine analogs. Rituximab also has a reasonable response rate in relapsed HCL; it can be given as a single agent sequentially after purine nucleosides or concurrently. Immunotoxins have robust responses but remain in development. Targeting the BRAF pathway will be an exciting future area of research. Many patients have minimal residual disease after initial treatment, but the clinical significance of this remains unknown.


Xi L, Arons E, Navarro W, et al.
Both variant and IGHV4-34-expressing hairy cell leukemia lack the BRAF V600E mutation.
Blood. 2012; 119(14):3330-2 [PubMed] Free Access to Full Article
Recently, the BRAF V600E mutation was reported in all cases of hairy cell leukemia (HCL) but not in other peripheral B-cell neoplasms. We wished to confirm these results and assess BRAF status in well-characterized cases of HCL associated with poor prognosis, including the immunophenotypically defined HCL variant (HCLv) and HCL expressing the IGHV4-34 immunoglobulin rearrangement. Fifty-three classic HCL (HCLc) and 16 HCLv cases were analyzed for BRAF, including 5 HCLc and 8 HCLv expressing IGHV4-34. BRAF was mutated in 42 (79%) HCLc, but wild-type in 11 (21%) HCLc and 16 (100%) HCLv. All 13 IGHV4-34(+) HCLs were wild-type. IGHV gene usage in the 11 HCLc BRAF wild-type cases included 5 IGHV4-34, 5 other, and 1 unknown. Our results suggest that HCLv and IGHV4-34(+) HCLs have a different pathogenesis than HCLc and that a significant minority of other HCLc are also wild-type for BRAF V600.


Blombery PA, Wong SQ, Hewitt CA, et al.
Detection of BRAF mutations in patients with hairy cell leukemia and related lymphoproliferative disorders.
Haematologica. 2012; 97(5):780-3 [PubMed] Free Access to Full Article
Hairy cell leukemia has been shown to be strongly associated with the BRAF V600E mutation. We screened 59 unenriched archived bone marrow aspirate and peripheral blood samples from 51 patients with hairy cell leukemia using high resolution melting analysis and confirmatory Sanger sequencing. The BRAF V600E mutation was detected in 38 samples (from 36 patients). The BRAF V600E mutation was detected in all samples with disease involvement above the limit of sensitivity of the techniques used. Thirty-three of 34 samples from other hematologic malignancies were negative for BRAF mutations. A BRAF K601E mutation was detected in a patient with splenic marginal zone lymphoma. Our data support the recent finding of a disease defining point mutation in hairy cell leukemia. Furthermore, high resolution melting with confirmatory Sanger sequencing are useful methods that can be employed in routine diagnostic laboratories to detect BRAF mutations in patients with hairy cell leukemia and related lymphoproliferative disorders.


Jones G, Parry-Jones N, Wilkins B, et al.
Revised guidelines for the diagnosis and management of hairy cell leukaemia and hairy cell leukaemia variant*.
Br J Haematol. 2012; 156(2):186-95 [PubMed]
The British Committee for Standards in Haematology first produced guidelines for the diagnosis and management of hairy cell leukaemia and hairy cell leukaemia variant in 2000. This revision updates those guidelines and covers the areas of diagnosis, treatment and assessment of response to therapy.


Arcaini L, Zibellini S, Boveri E, et al.
The BRAF V600E mutation in hairy cell leukemia and other mature B-cell neoplasms.
Blood. 2012; 119(1):188-91 [PubMed]
The somatically acquired V600E mutation of the BRAF gene has been recently described as a molecular marker of hairy cell leukemia (HCL). We developed an allele-specific PCR for this mutation and studied 62 patients with HCL, 1 with HCL variant, 91 with splenic marginal zone lymphoma, 29 with Waldenström macroglobulinemia, and 57 with B-cell chronic lymphoproliferative disorders. The BRAF V600E mutation was detected in all HCL cases and in only 2 of the remaining 178 patients. These 2 subjects had B-cell chronic lymphoproliferative disorders that did not fulfill the diagnostic criteria for HCL. Despite the positive PCR finding, the mutation could not be detected by Sanger sequencing in these 2 cases, suggesting that it was associated with a small subclone. We conclude that the BRAF V600E mutation is present in all patients with HCL and that, in combination with clinical and morphologic features, represents a reliable molecular marker for this condition.


Ganzel C, Gatt ME, Maly A, et al.
High incidence of skin rash in patients with hairy cell leukemia treated with cladribine.
Leuk Lymphoma. 2012; 53(6):1169-73 [PubMed]
Treatment of hairy cell leukemia (HCL) with cladribine induces durable remissions. Common toxicities are myelosuppression and immunosuppression with low counts of CD4 + T cells. Skin rash (SR) is seldom described. We collected clinical and laboratory data of 35 patients with HCL treated in Hadassah between January 1999 and February 2010, in order to evaluate the frequency and characteristics of SR after treatment with cladribine. We found a high frequency of SR in our group of patients (18/35 patients, 51%), mostly related to febrile neutropenia and concomitant treatment with penicillins/trimethoprim-sulfamethoxazole (TMP-SMZ). The lymphocyte count was low in all patients with SR. We conclude that patients with HCL treated with cladribine have an increased rate of drug hypersensitivity, possibly due to T-cell imbalance induced by cladribine. Since TMP-SMZ and penicillins are related to SR in most cases and are important in the management of patients with HCL, a desensitization protocol should be considered. Rechallenge may be safe after immune reconstitution.


Tiacci E, Schiavoni G, Forconi F, et al.
Simple genetic diagnosis of hairy cell leukemia by sensitive detection of the BRAF-V600E mutation.
Blood. 2012; 119(1):192-5 [PubMed]
Hairy cell leukemia (HCL) is a distinct clinicopathologic entity that responds well to purine analogs but is sometimes difficult to differentiate from HCL-like disorders (e.g., splenic marginal zone lymphoma and HCL variant). We recently identified the BRAF-V600E mutation as the disease-defining genetic event in HCL. In this study, we describe a new, simple, and inexpensive test for genetics-based diagnosis of HCL in whole-blood samples that detects BRAF-V600E through a sensitive allele-specific PCR qualitative assay followed by agarose-gel electrophoresis. This approach detected BRAF-V600E in all 123 leukemic HCL samples investigated containing as few as 0.1% leukemic cells. BRAF-V600E was detected at different time points during the disease course, even after therapy, pointing to its pivotal role in HCL pathogenesis and maintenance of the leukemic clone. Conversely, 115 non-HCL chronic B-cell neoplasms, including 79 HCL-like disorders, were invariably negative for BRAF-V600E. This molecular assay is a powerful tool for improving the diagnostic accuracy in HCL.


Boury S, Morgeson JS
Dyspnea, pancytopenia, and splenomegaly.
J Fam Pract. 2011; 60(10):593-6 [PubMed]
An extensive initial laboratory assessment, including testing for viral disorders, left the diagnosis unsolved.


Venkataraman G, Aguhar C, Kreitman RJ, et al.
Characteristic CD103 and CD123 expression pattern defines hairy cell leukemia: usefulness of CD123 and CD103 in the diagnosis of mature B-cell lymphoproliferative disorders.
Am J Clin Pathol. 2011; 136(4):625-30 [PubMed]
By using flow cytometry, we studied CD103 and CD123 expression by the malignant cells in 300 B-cell lymphoproliferative disorder (BC-LPD) cases, including 114 hairy cell leukemia (HCL), 20 HCL variant (HCLv), 9 splenic marginal zone lymphoma (SMZL; in 5, only CD103 was evaluated), 133 chronic lymphocytic leukemia (CLL), 3 follicular lymphoma (FL), and 21 mantle cell lymphoma (MCL). All HCLs expressed uniform CD103 and bright CD123. Among the 20 HCLv cases, 20 (100%) were CD103+ and 8 (40%) were CD123+ (partial or dim). CD103 was negative in all MCL, FL, CLL, and SMZL cases. CD123 was positive in 1 (25%) of 4 SMZL, 3.8% of CLL (5/133), 7 (33%) of 21 MCL, and 1 (33%) of 3 FL cases. CD103 is specific for HCL and HCLv. CD123 expression is more widespread in BC-LPDs but is useful in conjunction with CD25 to differentiate HCLv from HCL. These findings support the usefulness of CD123 and CD103 to aid in the differential diagnosis of BC-LPDs.


Boyd EM, Bench AJ, van 't Veer MB, et al.
High resolution melting analysis for detection of BRAF exon 15 mutations in hairy cell leukaemia and other lymphoid malignancies.
Br J Haematol. 2011; 155(5):609-12 [PubMed]
The BRAF V600E mutation has recently been described in all cases of hairy cell leukaemia (HCL). We have developed and validated a rapid and sensitive high-resolution melting analysis (HRMA) assay that detects BRAF exon 15 mutations when hairy cells are as low as 5-10% in a sample. All 48 HCL patients were positive for the BRAF V600E mutation, while 114 non-HCL cases were all V600E negative. Interestingly, we detected a novel BRAF D594N mutation in one patient with multiple myeloma. The HRMA assay offers a useful tool to aid the laboratory diagnosis of HCL.


Kao HW, Dunn P, Kuo MC, et al.
Classical hairy cell leukemia and its variant: a 17-year retrospective survey in Taiwan Chinese.
Acta Haematol. 2011; 126(3):186-93 [PubMed]
BACKGROUND: Classical hairy cell leukemia (HCL-C) and its variant (HCL-V) are rare chronic B-cell lymphoproliferative disorders. Only a few reports in Chinese patients are available.
METHODS: We retrospectively reviewed 16 patients with HCL-C and HCL-V in Taiwan over a 17-year period.
RESULTS: Eight were HCL-C and 8 were HCL-V. All HCL accounted for 0.7% of all adult leukemias. Compared to HCL-V, HCL-C was characterized by profound leukopenia, monocytopenia, thrombocytopenia and fewer circulating hairy cells. One HCL-C and 2 HCL-V patients had second malignancies. Seven HCL-C patients achieved hematological remission after splenectomy (n = 1) or 2-chlorodeoxyadenosine (n = 6). Of the 8 HCL-V patients, 6 received splenic irradiation. Only one achieved complete remission and another had partial remission; relapse or disease progression was noted 13.4 or 25.7 months later, respectively. Two of three HCL-V patients who underwent splenectomy had stable disease. All patients with HCL-C were alive while 3 with HCL-V expired. Compared to HCL-C, HCL-V had a significantly shorter leukemia-free survival.
CONCLUSION: A relatively higher proportion of HCL-V in all HCL comparing to Westerners is observed. Second malignancies are common. With an inferior outcome and dismal response to most treatment, enrollment in a clinical trial should be considered for HCL-V.


Sherman MJ, Hanson CA, Hoyer JD
An assessment of the usefulness of immunohistochemical stains in the diagnosis of hairy cell leukemia.
Am J Clin Pathol. 2011; 136(3):390-9 [PubMed]
Annexin-1 and T-bet are recently described immunohistochemical stains that reportedly assist in the diagnosis of hairy cell leukemia (HCL). Our objective was to assess the sensitivity and specificity of a panel of immunohistochemical stains in distinguishing HCL from other B-cell neoplasms, particularly splenic and extranodal marginal zone lymphomas (SMZL and ENMZL, respectively). The study included 234 bone marrow biopsy specimens: 101 HCL, 13 SMZL, and 10 ENMZL cases were assessed with CD20, tartrate-resistant acid phosphatase (TRAP), DBA.44, a-1, T-bet, and cyclin D1, and 110 control cases were assessed with annexin-1 and T-bet. Our study showed that annexin-1 is a specific and sensitive marker for HCL; however, interpretation is limited by positivity within myeloid precursors. T-bet, DBA.44, and TRAP immunohistochemical stains lack sufficient sensitivity and specificity to differentiate HCL from either form of marginal zone lymphoma. However, our data suggest that the addition cyclin D1 to the immunostaining panel will increase the sensitivity and specificity of HCL diagnosis.


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