Updated on 20.02.2025

This category includes following disorders:

• Hairy Cell leukemia (HCL)
• Splenic Marginal Zone Lymphoma (SMZL)
• Splenic diffuse red pulp small B cell lymphoma (SDRPL)
• Splenic B cell lymphoma/ leukemia with prominent nucleoli (SBLPN)

Hairy Cell leukemia

Introduction:                                      

• It is a neoplasm of small B-lymphoid cells with oval nuclei & abundant cytoplasm with hairy projections, diffusely infiltrating bone marrow & splenic red pulp, strongly expressing CD103, CD22 & CD11c and characterized by presence of BRAF V600E mutation. 

Epidemiology: 

• 2% of lymphoid leukemias 
• Median age – 60 years 
• M : F – 5 : 1 

Etiology: Exact etiology is not known

• Radiation 
• Organic solvents 
• BRAF-V600E- mutation is seen in all cases of HCL 

Pathogenesis: 

1.

BRAF-V600E mutation

↓

Constitutive activation of the kinase BRAF

↓

Downstream signaling through MEK/ERK pathway 

↓

Phosphorylation of several targets in the nucleus and cytoplasm

• Upregulation of General RAF-MEK-ERK Pathway Targets: MAFF, CCND1, ETV5, DUSP6, EGF1, SPRY2
• Upregulation of Proteins Characteristic of HCL: CD25 (IL2RA) and TRAP (ACP5)
• Induction of the HCL-Specific Gene Expression Signature: ACTB, CCND1, THBS1, AIF1, SPRY2, and others
• Induction of hairy morphology and inhibition of apoptosis

2.

Altered expression of chemokine and adhesion receptors + Over production of TNF, IL6 and BCL2

↓

Malignant transformation of mature memory B cell

↓

Homing into BM via constitutively activated integrin receptors and over-expression of matrix metalloprotease inhibitors

↓

Release of fibroblast growth factor and transforming growth factor beta 1 from hairy cells

↓

Increased fibronectin production in BM

↓

Reticulin fibrosis

Clinical Features: 

• Asymptomatic
• Massive splenomegaly- 60-70% cases 
• Rarely hepatomegaly, lymphadenopathy 
• Pancytopenia 
  • Anemia 
  • Neutropenia – Frequent infections 
  • Thrombocytopenia – Bleeding tendency 
• Common infections: 
  • Bacteria: M. avium intracellularae, Staphylococcus, Strep. pneumoniae, E. Coli, Pseudomonas aerogenosa.
  • Others: CMV, PCP, Aspergillus, histoplasma, cryptococcus. Listeria, Toxoplasma 
• Rare manifestations: 
  • Cutaneous vasculitis 
  • Leukocytoclastic angiitis 
  • Erythema nodosum 
  • Pulmonary infiltrates 
  • Polyarthritis 
  • Raynaud's phenomenon 
  • Osteolytic painful bony lesions (commonly involving proximal femur)

Investigations: 

• Hemogram:
  • Pancytopenia.
  • Monocytopenia is a constant feature
  • Hairy cells- Small to medium sized cells (usually twice the size of mature lymphocyte). Nucleus is oval / indented with homogeneous, spongy ground glass chromatin. Nucleoli are typically absent. Cytoplasm is abundant and pale blue. Circumferential hairy projections are present (Villous outlines). Discrete vacuoles are present.
• Bone marrow aspiration and biopsy
  • Aspiration, as a rule, unsuccessful 
  • Interstitial or patchy involvement by tumour cells is noted
  • Some preservation of fat and hematopoietic cells is present 
  • Leukemic cells- Widely spaced lymphoid cells creating a “honey comb” appearance 
  • Nucleus – Bean / round/ oval shaped 
  • Cytoplasm – Abundant with prominent cell borders (Fried egg appearance) 
  • Increased reticulin fibres (may result in a dry tap) 
  • Sometimes bone marrow can be hypoplastic due to cytokines produced by hairy cells 
• Cytochemistry 
  • Tartrate resistant acid phosphates (TRAP)- Positive (Isoenzyme 5 acid phosphatase present in hairy cell cytoplasm resists decolorization by tartrate)
• Electron microscopy: 
  • Rod shaped inclusions that represent ribosome lamellar complexes are seen. 
  • Circumferential cytoplasmic projections 
• Immunophenotype: 
  • Monocytic gate/ sometimes lymphocytic gate 
  • Positive – SIg M, B cell associated antigens (CD19, CD20, CD22, CD79a, CD200), CD11C, CD25, FMC7, CD103, CD123, Cyclin D, T bet (TBX-21)
  • Negative - CD5, CD10, CD23, CD79b, CD21, CD27, CD38 
  • Tissue section- Positive for CD20, DBA 44, TRAP, CD72, Annexin A1 (Most specific), BRAF mutant protein, Cyclin D1, SOX11 
• Cytogenetics 
  • No specific cytogenetic abnormality (Chromosome 5 is involved in 50% cases) 
• Molecular studies
  • Rearrangement of Ig light and heavy chains 
  • Over expression of Cyclin D1 
  • Molecular analysis for IGHV-34 gene rearrangements: 10% of HCL with typical immunophenotyping features have this arrangement. They lack BRAF mutation and behave like HCL variant. They have poor prognosis 
• IHC or molecular analysis (NGS) for BRAF V600E mutation- If classical immunophenotyping features are not seen  
   

Criteria for diagnosis:

Essential:

• Characteristic morphology in blood or bone marrow
• Strong positivity for CD20 and Annexin-1 by immunohistochemistry or coexpression of CD20/CD11c/CD103/CD25 by flow cytometry and/or immunohistochemistry.

Desirable:

• Clonal BRAF p.V600E (NP_004324.2) mutation.
• Useful adjuncts are the expression of CD123, bright CD22, bright CD200, bright surface immunoglobulins, cyclin-D1, and TBX21/T-Bet.

Prognosis: 

• Without treatment median survival is 5-10 years 
• With therapy- 4-year survival is up to 96%  
• Remission rate with purine analogues is more than 90% and average duration of remission is 15 years. 
• Modern therapy cannot cure this disease but can prolong the survival to near normal lifespan.
• Poor prognostic factors: 
  • Heavy BM involvement 
  • Massive splenomegaly 
  • Abdominal lymphadenopathy 
  • High beta 2 microglobulin
  • Increased LDH
  • CD38 expression
  • Mutated IGHV
  • Poor response to purine analogue 

Differential Diagnosis: 

• Splenic lymphoma with villous lymphocytes 
• Marginal zone B-cell lymphoma 
• Monocytoid B-cell lymphoma 
• Small lymphocytic lymphoma 
• Primary splenic chronic lymphocytic leukemia 
• Lymphoplasmacytoid lymphoma 
• Chronic lymphocytic leukemia 
• Mantle zone (intermediate) lymphoma 
• Myeloproliferative disorders 
• Malignant histiocytosis 
• Primary lymphoma of spleen 
• Chronic prolymphocytic leukemia 
• Large granular lymphocytic leukemia 
• Systemic mast cell disease 
• Hairy B-cell lymphoproliferative disorder 

Indications for Treatment: 

• Systemic symptoms such as weight loss (>10% within 6 months), excessive fatigue 
• Splenic discomfort 
• Recurrent infections 
• Hemoglobin <10g/dL 
• Platelets <1,00,000/cmm 
• ANC- <1000/cmm 
• Symptomatic organomegaly 
• Progressive lymphocytosis or lymphadenopathy  
• Bone involvement 

Pretreatment Work-up: 

• History 
  • B-Symptoms 
• Examination 
  • LN: 
  • Spleen: 
• WHO P. S. 
• BSA 
• Hemoglobin 
• TLC, DLC 
• Platelet count 
• BMA and Bx 
• IHC/Flow cytometry 
• IHC for mutant BRAF protein (VE1) 
• PCR/ NGS for BRAF V600E mutation
• CT (CAP) 
• Stage 
• LFT: Bili- T/D       SGPT:      SGOT: Albumin:     Globulin: 
• Creatinine 
• Electrolytes: Na:        K:       Ca: Mg:           PO4:     
• Uric acid: 
• LDH 
• HIV:                         
• HBsAg:                                
• HCV: 
• UPT  
• Cytogenetics
• Chemotherapy consent after informing about disease, prognosis, cost of therapy, side effects, hygiene, food and contraception
• Fertility preservation
• PICC line insertion and Chest X ray after line insertion
• Tumor board meeting and decision
• Attach supportive care drug sheet
• Inform primary care physician

Treatment Plan:

Response Criteria (Assessment must be done 4-6 months after Cladribine therapy): 

• Complete response: 
  • Near normalization of peripheral blood counts (Hb>11gm/dL, PL >1lac/cmm, ANC >1500/cmm) 
  • Regression of splenomegaly on physical examination 
  • Absence of morphological evidence of HCL on both PS and BMA. 
• Partial remission: 
  • Normalization of cytopenias along with minimum 50% improvement in both organomegaly and BM infiltration with no circulating hairy cells 

About Each Modality of Treatment: 

• Cladribine (+/- Rituximab)
  • 2 dosing regimens:
    • 0.14mg/kg/day- IV- over 2 hrs-OD- for 5 days
    • 0.1mg/kg/ Day- as continuous IV infusion for 7days  
  • 90% have chronic remission 
  • 26% relapse at median of 29 months 
  • Treat active life threatening or chronic infections prior to starting chemotherapy.
  • G-CSF may be used after cladribine to decrease the period of neutropenia
  • If Rituximab is being added, start it 1-2 months after completion of cladribine. Give Weekly for 8 weeks.
• Interferon alfa 2b 
  • Given for 1 year 
  • Rarely used 
  • Useful in patients with active infections 
  • 5% CR and 70% PR 
• Pentostatin 
  • Acts by inhibiting adenosine deaminase 
  • 4mg/m2 every 2 weeks until maximal response (usually 8-10 injections) then 2 extra injections 
  • Given for 3-6 months 
  • Produces neurotoxicity and skin rash 
  • Avoid if creatinine clearance is <60 ml/min, 50% dose if 40-60 ml/min 
• Splenectomy 
  • Improves quality of life and prolongs survival 
  • 75% response rate 
  • Indications 
    • Uncontrolled infections: As post-splenectomy rise in ANC can control infections effectively 
    • Increase in size >10cm below costal line with very less bone marrow involvement 
  • Alternate treatment should be considered 6 months after splenectomy 
• Rituximab 
  • Useful in relapsed cases 
  • 375mg/m2 IV weekly with purine analogues for 8 weeks 
• Moxetumumab pasudotox 
  • Recombinant immunotoxin directed against CD22 and linked to a truncated Pseudomonas exotoxin. 
  • Response rate- 86% in heavily pretreated patients. 
  • Dose: 40micrograms/kg-IV- Given on days 1, 3, and 5 of each 28 days cycle for up to 6 cycles (Stop if CR is achieved)
  • Good pre-hydration should be given. 
  • Side effects- Hemolytic uremic syndrome, capillary leak syndrome. 
  • Moxe retreatment is also effective
• BRAF-MEK-ERK pathway inhibitors 
  • Vemurafenib- 
    • 960mg- BD- daily for 16-18 weeks 
    • Response rate- 96% 
    • Side effects- Skin rash, palmar/plantar fibrosis, skin warts, skin tumors, arthritis 
    • When Rituximab is added, it is given once in 2 weeks for 8 doses
  • Dabrafenib
    • Dose: 150mg- BD for 8 weeks (additional 4 weeks for patients who do not achieve CR)
    • ORR: 80%
  • Trametinib
    • Dose: 2mg- OD
    • Usually combined with Dabrafenib
• Ibrutinib:
  • Dose: 420mg- OD
  • ORR- 24% (In heavily pretreated patients)
• Venetoclax
  • Each cycle of 28 days for up to 12 cycles.
  • May be added with Rituximab

Supportive Care: 

• Herpes virus prophylaxis is must during treatment and 3 months thereafter (until CD4 count >200/cmm) 
• PCP prophylaxis for same duration 
• Give only irradiated blood products lifelong if patients are treated with purine analogues 
• Radiation for lytic bone lesion (1500-3000 rads) 

Monitoring After Treatment/ Follow-up: 

• Long term survivors are at increased risk of HD, NHL and thyroid malignancies 

Special Situations: 

• Pregnancy: 
  • Avoid chemotherapy as far as possible. If inevitable, INF is a reasonable choice. 

Related Disorders: 

• Blastic variant of HCL 
  • Massive splenomegaly 
  • Peripheral adenopathy and cytopenias 
  • TRAP- Positive, MPO- Negative 

Splenic Marginal Zone Lymphoma

Introduction: 

• It is a B-cell neoplasm comprising of small lymphocytes which surround and replace the splenic white pulp germinal centers, efface the follicle mantle and merge with a peripheral zone of larger cells including scattered transformed blasts; both small and large cell infiltrate the red pulp. 
• It is also called as splenic lymphoma with villous lymphocytes. 

Epidemiology: 

• 2% of lymphoid neoplasms 
• Median age- 69 years 
• M:F- 1:1 

Etiology: 

• HCV infection 

Pathogenesis:

• NOTCH pathway and other marginal zone differentiation-associated genes are frequently mutated
• Mutations involving the KLF2 transcription factor, leading to activation of NF-kB signaling

Clinical Features: 

• Splenomegaly 
• B Symptoms  
• Autoimmune manifestations
  • Acquired angioedema due to C1-esterase inhibitor deficiency
  • Cold agglutinin disease and warm antibody autoimmune haemolytic anaemia
  • Immune thrombocytopenia
  • Mixed cryoglobulinemia

Investigations: 

• Peripheral smear- Small lymphoma cells which have a characteristic short polar villi (confined to one pole) & irregular membrane outline. Nucleolus is seen in half of cases 
• Bone marrow aspiration: 
  • Similar cells infiltrate in nodular/ interstitial pattern 
  • Intrasinusoidal lymphocytic infiltration is characteristic 
• Immunophenotype 
  • Positive - Surface IgM& IgD, CD20, CD79a, CD11c , PAX5, FMC7, CD27, CD38 (dim)
  • Negative - CD5, CD10, CD23,  Annexin A1, Nuclear Cyclin D1, CD103, CD10, BCL6, SOX11, LEF1
  • Variable- CD23, CD43, DBA44, CD25
  • Ki 67 staining- Targetoid pattern with increased growth fraction in both germinal and marginal zones 
• Molecular studies
  • Rearrangement of Ig heavy and light chain genes. 
  • Loss of Chr. 7q 31-32 which leads to inactivation of p53 
  • Trisomies of chromosome 3 and 18
  • Dysregulation of CDK gene on 7q21  
  • Mutations in KLF2 and NOTCH2 genes
• S. Protein electrophoresis- Some may have small monoclonal M protein 

Criteria for Diagnosis: 

Essential:

• Small B-cell lymphoma involving bone marrow and/or peripheral blood composed of small lymphoid cells with villous processes
• Neoplastic cells express pan-B cell markers, IgM and IgD and are negative for BCL6, annexin A1, CD103, cyclin D1, SOX11 and LEF1
• Other splenic and nodal B-cell lymphomas should be excluded.
• Clinical or imaging studies that show splenomegaly.

Desirable:

• Neoplastic cells negative for CD5 and CD10

Prognosis: 

• It has an indolent course, with median survival- >10 years
• Prognostic markers:
  • Hemoglobin: <12gm/dL
  • Elevated LDH
  • Albumin- <3.5g/dL

Differential Diagnosis: 

• CLL 
• HCL 
• Mantle cell lymphoma 
• Follicular lymphoma 
• Lymphoplasmacytic lymphoma 

Indications for Treatment (Even at relapse): 

• Symptomatic patient (weight loss >10% in <6 months, fever, drenching sweats)
• Progressive/ symptomatic spenomegaly
• Bulky lymphadenopathy
• Autoimmune phenomenon
• Progressive cytopenia 
• Compromised vital organs
• Hepatitis C positive with splenomegaly 

Pretreatment Work-up: 

• History  
  • B-Symptoms  
• Examination  
  • LN:  
  • Spleen:  
• WHO P. S.  
• BSA  
• IHC/Flow cytometry  
• BMA and Bx  
• CT (CAP)  Or Whole body PET if transformation is suspected
• Stage  
• Hemoglobin  
• TLC, DLC  
• Platelet count  
• LFT:  Bili- T/D      SGPT:         SGOT:  Albumin:         Globulin:  
• SPEP/ IFEP 
• Creatinine  
• Electrolytes: Na:     K:    Ca:  Mg:       PO4:        
• Uric acid:  
• LDH  
• HIV:                         
• HBsAg:                                
• HCV:  
• UPT  
• Sperm banking
• Cytogenetics  
• ECHO(If anthracyclines planned)- LVEF-              %
• Chemotherapy consent after informing about disease, prognosis, cost of therapy, side effects, hygiene, food and contraception
• Fertility preservation
• PICC line insertion and Chest X ray after line insertion
• Tumor board meeting and decision
• Attach supportive care drug sheet
• Inform primary care physician

Treatment Plan: 

Response Criteria: 

• Complete response: 
  • Recovery of counts 
  • Normal bone marrow with no excess lymphocytes 
  • Regression of splenomegaly 

About each modality of treatment:

• Splenectomy:
  • Useful in selected patients Ex: rituximab, BTK inhibitor refractory disease
  • Not useful if there is disseminated nodal involvement or BM involvement.
  • Laporoscopic approach is better
  • Vaccinations must be done 2 weeks prior to surgery
  • VTE prophylaxis should be given
• Chemotherapy:
  • BR is preferred over single agent Rituximab in patients with CD5 expression
• BTK inhibitors:
  • May be combined with Venetoclax or Rituximab
• CAR-T cell therapy
  • Axicabtagene ciloleucel: Useful in patients who have failed multiple lines of therapy

Monitoring After Treatment/ Follow-up: 

• Once in 3-6 months for 5 years, then once a year   

Splenic diffuse red pulp small B cell lymphoma (SDRPL)

• Diagnosis is made after excluding CLL, HCL, LPL, PLL, vHCL 
• Rare (<1% of all NHL)
• Present with massive splenomegaly 
• Peripheral smear shows small to medium sized villous lymphocytes (Similar to seen with SMZL) with leucopenia and thrombocytopenia 
• BM shows intrasinusoidal infiltration 
• Spleen- Diffuse pattern with red pulp involvement. Both cord and sinusoidal infiltration are present.
• TRAP- Negative 
• Immunophenotyping 
  • Positive- CD20, CD19, CD79a, DBA.44, IgG, Cyclin D3
  • Negative- IgD, Annexin 1, CD25, CD5, CD103, CD123, CD11c, CD10, CD23, CD43, cyclin D1, CD21, CD38
• SPE may show monoclonal band
• Molecular studies
  • Hypermutation in IgHV genes 
  • t(9:14) involving PAX5 and IgH @genes 
  • TP53 mutations 
• Criteria for diagnosis
  • Essential:
    • Diffuse infiltration of the spleen by monomorphic small B cells, accompanied by atrophic white pulp
    • Peripheral blood with circulating small cells with abundant cytoplasm, broad-based and unevenly distributed cytoplasmic villous projections are well-visible, and inconspicuous nucleolus
    • Immunophenotype compatible with SDRPL
  • Desirable:
    • Absence of BRAF p.V600E (NP_004324.2) mutation
    • Absence of lymphadenopathy other than splenic hilar lymph node involvement.
• Prognosis: Indolent course 
• Treatment:
  • Treat only if indication for treatment is present
  • First line: Splenectomy
  • Ineligible for splenectomry or R/R: Rituximab monotherapy, R+Cladribine, R+Bendamustine

Splenic B cell lymphoma/ leukemia with prominent nucleoli (SBLPN)

• Includes cases which were previously called hairy cell leukemia- variant and CD5 Negative B- Prolymphocytic leukemia.
• It is considered hydrid between hairy cell leukemia, B-prolymphocytic leukemia and marginal zone lymphoma 
• It is associated with high WBC count (50-80 x 109/L) and splenomegaly 
• Morphologically compared to HCL, cells are medium to large, have distinct, large, single nucleolus and round nucleus with irregular nuclear contours. Cytoplasm is abundant, basophilic and lacks hairy projections.
•  BM biopsy- Infiltrates are subtle and vary inconspicuous intra-sinusoidal infiltration 
• TRAP- Negative 
• BRAF V600E mutation- Negative
• MAP2K1 mutations- 50% of cases
• Cytogenetics: Complex karyotypes involving 14q32 as well as 8q24, deletion 17p, and trisomy 12
• Immunophenotyping 
  • Positive- CD103, CD11C, FMC7, surface immunoglobulin (more frequently IgG), pan-B cell antigens (CD19, CD20 and CD22, DBA-44)
  • Negative- CD25, CD123, Annexin 1, HC2, TRAP
• Criteria for diagnosis:
  • Essential
    • Circulating medium-sized lymphoid cells with prominent nucleoli or convoluted nuclei and absence of hairy projections
    • Presence of B-cell antigens CD19, CD20, CD79a, or PAX5;
    • Absence of characteristic phenotype of HCL, including expression of CD25, annexin A1, cyclin D1, and TRAP.
  • Desirable
    • Diffuse involvement of the splenic red pulp with atrophic white pulp, but most cases are diagnosed without a spleen specimen;
    • Absence of BRAF mutation.
• Prognosis: Median survival- 9 years
• Treatment 
  • Treatment to be given only if indication for treatment is present (same as HCL)
  • They poorly respond to cladribine and pentostatin (Do not respond to IFN-alfa) 
  • Rituximab with Cladribine is the better option. 
  • Splenectomy- Good partial response in 2/3rd patients 
  • Options in relapse/ refractory situations: R-Bendamustine, Ibrutinib +/- Venetoclax

Immunophenotype by Immunohistochemistry

Immunophenotype by Flow Cytometry

Molecular Profile

Figures:

Figure 6.5.1- Hairy cell in peripheral smear

Figure 6.5.2- Hairy cell leukemia- Bone marrow biopsy

Recent advances:

Long-term outcomes in patients with relapsed or refractory hairy cell leukemia treated with vemurafenib monotherapy

Vemurafenib, an oral BRAF inhibitor, has demonstrated high response rates in relapsed/refractory (R/R) hairy cell leukemia (HCL). Present study reports results of 36 patients with R/R HCL treated with vemurafenib. The best overall response rate was 86%, including 33% complete response and 53% partial response. Overall survival was 82% at 4 years, with a significantly shorter OS in patients who relapsed within 1 year of initial treatment with vemurafenib. All adverse events in the retreatment cohort were grade 1/2 except for 1 case of a grade 3 rash and 1 grade 3 fever/pneumonia..

https://doi.org/10.1182/blood.2022016183

Venetoclax in Relapsed or Refractory Hairy-Cell Leukemia 

In 6 patients with hairy-cell leukemia and progressive disease after vemurafenib plus rituximab, 5 had a response to venetoclax alone or with the addition of rituximab, including 3 complete responses. 

https://doi.org/10.1056/NEJMc2216135 

Dabrafenib plus trametinib in patients with relapsed/refractory BRAF V600E mutation–positive hairy cell leukemia 

Patients received dabrafenib 150 mg twice daily plus trametinib 2 mg once daily until disease progression, unacceptable toxicity, or death. ORR was 89.0% and 65.5% of patients had a complete response. The 24-month DOR was 97.7% with 24-month PFS and OS rates of 94.4% and 94.5%, respectively. 

https://doi.org/10.1182/blood.2021013658