Histopathology of human lymph node tularemia caused by Francisella tularensis var palaearctica.

Histopathology of tularemia, caused by type-B strain, tuberculosis, and sarcoidosis were compared in lymph node biopsy specimens from ten patients with tularemia, 26 with tuberculosis, and 14 with sarcoidosis. In very early tularemia there were only reactive changes without necrosis. Abscess necrosis with or without epithelioid cell reaction was observed during the second week and caseous necrosis during the fourth week. Argyrophil fibers were absent from necrotic lesions in tularemia, but, often, also in tuberculosis. In most cases of tularemia and in half the cases of tuberculosis, the inflammatory process extended beyond the capsule of the lymph node. In some cases, tularemia could not be histologically differentiated from tuberculosis, but tularemia was always differentiated from sarcoidosis. Our series of lymph node tularemia seems to represent a milder disease than those cases published earlier. Tularemia should be considered in the differential diagnosis with tuberculosis, toxoplasmosis, and cat-scratch disease.