Non-Hodgkin's Lymphoma (NHL) results from the malignant proliferation of cells of lymphocytic lineage. Although malignant lymphomas are generally restricted to lymphoid tissue such as lymph nodes and spleen, it is not uncommon to find bone marrow involvement in children.

INCIDENCE AND EPIDEMIOLOGY

Incidence

• NHL accounts for 5-7% of malignant diseases in childhood (Europe, United States). It is the third most common childhood malignancy
  
  
• The incidence of NHL is higher in the Middle East, Nigeria, and Uganda (15 of 100,000 children under 5-10 years of age).
  
  
• NHL accounts for 60% of all childhood lymphomas
  
  
• Isolated cases of familial NHL have been known to occur.

Epidemiology

• Sex : M:F= 2.5:1
  
  
• Age : Peak age 5-15 years
  
  
• Risk factors :-
  
  
  • Genetic- Immunological defects (Bruton's type of sex-linked agammaglobulinemia, common variable agammaglobulinemia, ataxia telangiectasia, Wiskott-Aldrich syndrome, severe combined immune deficiency)
    
    
  • Post-transplant immunosuppression - Post-bone marrow transplantation (especially with use of T-cell depleted marrow); post-liver or post-heart transplantation.
    
    
• Drugs : Diphenylhydantoin
  
  
• Radiation : Children treated with chemo-radiotherapy for Hodgkin's disease
  
  
• Virus : Epstein-Barr virus (EBV), human immune deficiency virus (HIV)

PATHOLOGIC CLASSIFICATION

Table 1 : Revised European-American Lymphoma Classification from the International Lymphoma Study Group

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B-cell neoplasms

Precursor B-cell neoplasms

Precursor B-lymphoblastic leukemia / lymphoma

Peripheral B-cell neoplasms

• B-cell CLL / PLL / SLL
  
  
• Lymphoplasmacytoid lymphoma / immunocytoma
  
  
• Mantle cell lymphoma
  
  
• Follicle center lymphoma, follicular
  
  
  • Provisional cytologic grades: I (small), II (mixed), III (large)
    
    
  • Provisional subtype: diffuse, predominantly small cell
    
    
• Marginal zone B-cell lymphoma
  
  
  • Extranodal (MALT ± monocytoid B cells)
    
    
  • Provisional category: nodal (± monocytoid B cells)
    
    
• Provisional entity : splenic marginal zone lymphoma
  
  
• Hairy cell leukemia
  
  
• Plasmacytoma / myeloma
  
  
• Diffuse large B-cell lymphoma
  
  
• Burkitt's lymphoma
  
  
• Provisional entity: high-grade B-cell lymphoma, Burkitt-type
  
  

T-cell and putative natural killer (NK) cell neoplasms

• Precursor T-cell neoplasms
  
  
• Precursor T-lymphoblastic lymphoma / leukemia
  
  
• Peripheral T-cell and NK cell neoplasms
  
  
  • T-cell CLL / PLL
    
    
  • Large granular lymphocyte leukemia
    
    
  • Mycosis fungoides / Sezary syndrome
    
    
  • Peripheral T-cell lymphomas, unspecified
    
    
• Provisional categories: medium, mixed, large, lymphoepitheloid
  
  
• Provisional subtypes :
  
  
  • Hepatosplenic T-cell lymphoma
    
    
• Subcutaneous panniculitic T-cell lymphoma
  
  
  • Adult T-cell lymphoma / leukemia
    
    
  • Angioimmunoblastic T-cell lymphoma
    
    
  • Angiocentric lymphoma
    
    
  • Intestinal T-cell lymphoma (± enteropathy)
    
    
  • Anaplastic large cell lymphoma (T/null)
    
    
  • Provisional ALCL Hodgkin's-like
    
    

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Note : CLL, chronic lymphocytic leukemia; PLL prolymphocytic leukemia; SLL, small lymphocytic lymphoma, MALT,mucosal associated lymphoid tissue lymphoma; ALCL, anaplastic large cell lymphoma

From Harris NL, Jaffe ES, Stein H, Banks PM,Chan JKS, Cleary ML, Delsol G et al. A revised European-American classification of lymphoid neoplasms: a proposal from the International Lymphoma Study Group, Blood 1994, 84: 1361-92.

Fifty percent of NHL in children are small noncleaved, 30% lymphoblastic, and 20% large cell types.