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Infective Conditions of the Lymph Node (Lymphadenitis)

(This is another continuation of the Sabah Lymphoma talk -- first and second part)

I. Toxoplasma

  • Three features:
    • Follicular hyperplasia.
    • Epithelioid histiocytes.
    • Monocytoid B cells in sinusoids.
  • Enlarged germinal centre (still have mantle zone and tingible body macrophages)
II. Viral
  • Partial architectural effacement with expanded paracortex.
  • Polymorphous cellularity.
  • Mottled histological appearance with marked follicular hyperplasia.
  1. Infectious mononucleosis
    • Expanded paracortez with heterogenous population.
    • Increased blood vessels.
    • Presence of immunoblasts that mimic Reed-Sternberg cells.
    • Hyperplastic follicles.
  2. Herpes simplex virus
    • Mixed cell population.
    • Reed-Sternberg-;ole activated lymphocytes.
    • Apoptotic cells and neutrophils.
  3. HIV
    • Early: present with acute reactive lymphadenitis.
    • Late: present with marked CD4+ T-cell depletion, and involution of lymph nodes.
    • 3 phases:
      1. Acute
        • Non-specific, more to viral lymphadenitis, eg paracortical expansion.
      2. Transition
        • Disruption of normal architecture, germinal centre smaller, excessive pool of blood vessels.
      3. Burn-out
        • Atrophic.
III. Bacterial
  • Composed of sinus expansion.
  • May contain proteinaceous fluids or microabscesses
  • eg Cat-scratch disease, tuberculosis.
Below is not an infective condition but important anyway:

Epithelial cell inclusion in lymph node
  • May include squamous, thyroid, mammary glands
  • Must differentiate from metastasis.
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