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Non Hodgkin’s Lymphoma (NHL)

  • Neoplastic clonal proliferations of lymphocytes
    • Can involve LNs, extranodal tissues, or both
  • Usually systemic, widely disseminated diseases
  • Can be tumours of B or T lymphocytes – B cell tumours MC in US

Epidemiology

  • MC in Caucasian men
  • MC in 60-70 year olds
  • NHLs in children tend to be more aggressive

Etiology

  • Genetic predisposition – increased incidence in people with inherited immunodeficiency disorders
    • E.g. ataxia-telangiectasia, Wiskott-Aldrich syndrome (XLR disorder characterised by eczema, thrombocytopenia and immune deficiency)
  • Pesticides, herbicides
  • Viruses – EBV, HTLV-1, HCV
    • EBV infects and immortalises B cells and stimulates B cell replication
  • Immunosuppression – predisposes to NHL e.g. HIV

Cytogenetics

  • In normal development the genes for lymphocyte antigen receptors (Igs for B-cells, TCR for T-cells) go through a process of genetic recombination
  • In this process reciprocal translocations can occur, predisposing to NHL and other malignancies

Classification – see WHO classification at end

  • Two most common are
    • Diffuse large B-cell lymphomas
    • Follicular lymphomas, t(14:18)
Clinical Features

 

Staging

Indolent vs Aggressive NHLs

Prognostic factors – summarised in the International NHL Prognostic Index

Diagnosis

  • Histology
  • Immunophenotyping – by flowcytometry
    • Detection of Ig light chain restriction (imbalance in expression of κ and λ light chains on lymphocytes, rather than the normal 2:1 ratio of κ to λ) suggests a clonal B-cell population – i.e. a B-cell malignancy
  • Cytogenetics
  • Antigen receptor gene rearrangement studies
  • Excision biopsy w/ immunohistchem

Specific lymphoma types

Diffuse large B-cell lymphomas – MC type of lymphoma

  • Most aggressive if untreated
  • Variable histologic appearance
  • If CD-20 +ve use rituximab

Follicular lymphomas

  • Subdivided into 4 histologic grades
    • Follicular, predominantly small cleaved cell (grade I)
    • Follicular, mixed small cleaved and large cell (grade II)
    • Follicular, predominantly large cell (grade III)
  • Grade I + II are indolent with long survival
  • Translocation [t(14;15)] – over expression of BCL-2, inhibits apoptosis

Small lymphocytic lymphoma

  • Tissue based equivalent of CLL – only distinction is based on absence of lymphocytosis in SLL (<5000 ly/μL)
  • Low grade
  • Expresses CD5 (T-cell marker) – only other B-cell lymphoma to express CD5 is mantle cell lymphoma

Lymphoma of Mucosa-Associated lymphoid tissue (MALT)

  • MALT lymphomas are MC type of extranodal lymphoma – MC in stomach
    • Also in salivary glands, breasts, thyroid
  • Localised at diagnosis – systemic dissemination occurs late
  • Indolent
  • Relapses after therapy frequently occur at other MALT sites
  • Chronic gastritis caused by H.pylori is implicated in gastric MALT

Mantle cell lymphoma

  • MC in older males
  • Most cases are advanced at diagnosis, with BM involvement
  • Characterised by small cells with nuclear irregularity
  • Translocation [t(11;14)] is implicated
  • Expresses CD5

Burkitt’s lymphoma

  • Very high grade NHL
  • MC in Africa
  • MC in children
  • Burkitt cell leukemia – is the leukemic equivalent. Their behaviour and treatment are the same
  • Strong association with EBV and malaria in Africa
  • Universal association between BL and the translocation of the c-MYC proto-oncogene to one of the Ig gene (heavy or light chain)
    • t(8;14) – most common translocation
      • c-MYC on C8 is translocated to the Ig heavy chain gene on C14
      • over expression of c-MYC gene results in very high proliferation rate of cells
  • African presentation – big, rapidly growing jaw mass in young child
  • US presentation – most pts present with intra-abdominal disease

T-cell lymphomas

  • Most are peripheral T-cell lymphomas
  • Compared to B-cell lymphomas, those of T-cell have a higher incidence of extranodal disease and are at an advanced stage at diagnosis
  • Most are associated with B symptoms (systemic sx)
  • Worse prognosis

Treatment

Indolent lymphomas

  • Watch and wait if pt is asymptomatic
  • Chemotherapy
    • COPP – cyclophosphamide, oncovin (vincristine), prednisone, procarbazine
  • Radiation
  • Interferon
  • Fludarabine – for relapses
  • Rituximab – anti CD20

Aggressive lymphomas

  • Chemotherapy
    • CHOP – cyclophosphamide, hydroxydaunorubicin (doxorubicin), oncovin, prednisone
  • Radiation
  • Stem cell transplant

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