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Case  - Discussion

Hematopathology Case




Typical morphologic changes: reactive follicles (center and right-upper), clusters of epithelioid cells impinging follicles (center), and patches of monocytoid cells (left-lower).

Toxoplasma antibody Toxoplasma antibody

Diagnosis: Toxoplasmic lymphadenitis

Characteristic triad: Reactive follicles, clusters of epithelioid cells impinging follicles, and patches of monocytoid cells

Discussion: This node shows prominent reactive lymphoid follicles. Many small clusters of epithelioid histiocytes are present impinging or inside the follicles. Frequent clusters of monocytoid cells are noted. All these features are characteristic for toxoplasmic lymphadenitis. However, there are multiple large, well-defined granulomas with central necrosis; this finding is usually seen in cat scratch disease, but not toxoplasmic lymphadenitis. Later on, the patient was found to have 3 cats at home; maybe she was exposed to the infections from different cats.

Toxoplasmic Lymphadenitis

  • Toxoplasma gondii

  • Immunocompetent patients mostly present as solitary  posterior cervical lymphadenopathy

  • Self-limited, but severe complications in immunodeficient patients

  • Histology:

  • Florid follicular hyperplasia

  • Interfollicular epithelioid histiocytes, singly or in small clusters; may encroach on or present in germinal centers

  • Monocytoid B cells in a sinusoidal and parasinusoidal pattern

  • Usually lack of necrosis or well-formed granulomas

  • Cysts/intracellular organisms only rarely found

  • DDX: Leishmania lymphadenitis; early stages of cat-scratch disease, infectious mononucleosis, and CMV lymphadenitis