Toxoplasmosis

Synonyms: Piringer-Kuchinka Lymphadenitis

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Definition

Involvement of lymph node by a protozoan parasite Toxoplasma gondii infection.

Clinical Features

Common parasitic infection
Typically:
- posterior cervical nodes:
  - firm
  - moderately enlarged
- young woman1

Pathogenesis

Caused by protozoan parasite Toxoplasma gondii2

Histopathology

Nodal architecture rather well preserved
Typical triad:
- not present in all cases
- constituted by:
  - marked follicular hyperplasia:
    - intense mitotic activity
    - phagocytosis of nuclear debris
  - small granulomas:
    - composed almost entirely of epithelioid cells (Fig. 1
      Fig. 1: Toxoplasmosis of lymph node. Small noncaseating granulomas composed of epithelioid cells are located at the periphery of a hyperplastic follicle. This picture is almost pathognomonic of this disease.
      )
    - located within hyperplastic follicles
    - at periphery, encroaching on and blurring their margins
  - distention of marginal and cortical sinuses by monocytoid B cells (Fig. 2
    Fig. 2: Toxoplasmosis of lymph node. An area of massive monocytoid B-cell hyperplasia.
    )
- additional feature:
  - immunoblasts and plasma cells in medullary cords3
- variations of granuloma include:
  - necrosis
  - more than an occasional Langhans’ giant cell

Diagnosis

Confirm serologically:
- - may be normal in early stages7
Collections of epithelioid cells within germinal centers:
- seems to be a nearly specific feature for toxoplasmosis8

Other investigations

Extremely rare to find:
- Toxoplasma organisms by morphologic examination (Figs 3 and 4
  Fig. 3: Toxoplasma cyst as seen in a microscopic section. This is a very unusual finding in lymph nodes affected by the disease.
  Fig. 4: Toxoplasma cyst as seen in a touch preparation. This is a very unusual finding in lymph nodes affected by the disease.
  )
- Toxoplasma gondii genome by PCR:4,5
  - in contrast to results obtained in:
    - myocarditis 5
Serology:
- combination of microscopic features correlates with:6
  - Sabin–Feldman dye test
  - IgM immunofluorescent antibody test
- may be normal in early stages7

Differential Diagnosis

Select up to 2 differential diagnoses to compare with Toxoplasmosis

Other infectious diseases
Lymphocyte predominance Hodgkin's lymphoma

References

1 McCabe RE, Brooks RG, Dorfman RF, Remington JS. Clinical spectrum in 107 cases of toxoplasmic lymphadenopathy. Rev Infect Dis. 1987;9:754–774.

2 Hill D, Dubey JP. Toxoplasma gondii: transmission, diagnosis and preventation. Clin Microbial Infect. 2002;8:634–640.

3 Saxen L, Saxen E, Tenhunen A. The significance of histological diagnosis in glandular toxoplasmosis. Acta Pathol Microbiol Scand. 1962;56:284–294.

4 Bastien P. Molecular diagnosis of toxoplasmosis. Trans R Soc Trop Med Hyg. 2002;96:S205–S215.

5 Weiss LM, Chen YY, Berry GJ, Strickler JG, Dorfman RF, Warnke RA. Infrequent detection of Toxoplasma gondii genome in toxoplasmic lymphadenitis. A polymerase chain reaction study. Hum Pathol. 1992;23:154–158.

6 Dorfman RF, Remington JS. Value of lymph-node biopsy in the diagnosis of acute acquired toxoplasmosis. N Engl J Med. 1973;289:878–881.

7 Frenkel JK. Toxoplasmosis. Mechanisms of infection, laboratory diagnosis and management. Curr Top Pathol. 1971;54:28–75.

8 Miettinen M, Franssila K. Malignant lymphoma simulating lymph node toxoplasmosis. Histopathology. 1982;6:129–140.

Last updated: 23 Nov 2006