Non-Hodgkin Lymphoma

Non-Hodgkin Lymphoma is a topic covered in the 5-Minute Pediatric Consult.

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Basics

Description

  • Non-Hodgkin lymphoma (NHL) arises from the malignant proliferation of developing or mature B or T lymphocytes.
  • Extent of disease is determined using the Murphy staging system:
    • Stage I: single tumor (extranodal) or single nodal area, excluding mediastinum or abdomen
    • Stage II: single tumor with regional nodal involvement, two or more tumors or nodal areas on the same side of the diaphragm, or a primary GI tract tumor (resected) with or without regional node involvement
    • Stage III: tumors or lymph node (LN) areas on both sides of the diaphragm, any primary intrathoracic or extensive intra-abdominal disease (unresectable), or any paraspinal or epidural tumors
    • Stage IV: bone marrow or CNS disease regardless of other sites; marrow involvement defined as 0.5–25% malignant cells

Epidemiology

  • Third most common childhood malignancy (~12% cancers in individuals <20 years of age in developed countries)
  • Number of cases is increasing in adolescents and young adults.
  • Male-to-female ratio: 3:1

Incidence

  • 10 to 20 cases per 1 million children per year
  • Higher frequency of endemic Burkitt-type in equatorial African countries (10 to15 per 100,000 children <5 to 10 years)
  • Incidence increases steadily with age; in children, usually seen in 2nd decade of life (unusual in those <3 years of age)

Risk Factors

Environmental factors

  • Drugs: immunosuppressive therapy and diphenylhydantoin
  • Radiation: atomic bomb survivors and ionizing radiation
  • Viruses: Epstein-Barr virus (EBV) present in >95% of cases of endemic Burkitt versus <20% cases of sporadic; HIV

Genetics

Genetic predisposition: increased risk in patients with immunologic defects (e.g., Bruton agammaglobulinemia, ataxia telangiectasia, Wiskott-Aldrich, severe combined immunodeficiency [SCID], X-linked lymphoproliferative syndrome [XLP])

Pathophysiology

  • Unlike adults, low- and intermediate-grade NHL is uncommon in children (~7% of cases).
  • NHL in children and adolescent can be divided into three major categories according to the National Cancer Institute (NCI):
    • Mature B-cell NHL (Burkitt and Burkitt-like lymphoma, diffuse large B-cell lymphoma [DLBCL], primary mediastinal B-cell lymphoma)
      • 50% of childhood NHL
      • Express mature B-cell markers (CD20, surface immunoglobulin [Ig])
      • Terminal deoxynucleotidyl transferase (TdT) negative
      • Burkitt lymphoma has characteristic t(8;14), rarely t(8;22) or t(2;8); all chromosomal translocations involve the c-myc proto-oncogene.
      • DLBCL usually of the germinal center B-cell phenotype. Unlike adults, the t(14:18) translocation is rare.
    • Lymphoblastic lymphomas (LL)
      • 30% of childhood NHL
      • In children, 90% T-cell and 10% B-cell origin
      • Morphologically identical to acute lymphoblastic leukemia. TdT positive; express early T (CD5, CD7, cytoplasmic CD3) or B (CD19, CD10) cell markers. Bone marrow involvement of >25% blasts is considered leukemia.
      • Early thymic progenitor (ETP) subtype arises earlier in T-cell ontogeny. Most recent studies indicate it has a slower response to therapy but does not have a worse prognosis.
    • Anaplastic large cell lymphoma (ALCL) (mature T-cell or null-cell lymphomas):
      • 10% of childhood NHL
      • Express CD30 (Ki-1)
      • Contain chromosomal rearrangement involving the ALK gene (85% t2;5)
  • Immunodeficiency-associated NHL usually of B-cell origin

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