Mesenteric lymphadenitis due to Yersinia enterocolitica.

The histopathological diagnosis of Yersinia enterocolitica infections in mesenteric lymph nodes is described on the basis of biopsy material from 14 cases collected at the Lymph Node Registry in Kiel. In all cases, the aetiological diagnosis was verified by demonstrating significant antibody titres in serological tests and, in two cases, by isolating Yersinia enterocolitica from faeces. The mesenteric lymph nodes showed a rather specific histological picture. In all cases, the capsule was thickened by oedema and stained metachromatically. The cortical and paracortical pulp was always hyperplastic owing to an increase in the number of immunoblasts, plasmablasts, and plasma cells. The sinuses were dilated and filled with intensely basophilic cells that varied in size from small to large (plasmacytoid cells and precursors). Small, or relatively large accumulations of "immature histiocytes" (transformed lymphocytes) were seen in the sinuses in about two thirds of the cases. Occasionally, there were small foci of small histiocytes (emigrated monocytes) in the cortical pulp. An abscess similar to the abscesses found in abscess-forming reticulocytic lymphadenitis due to Yersinia pseudotuberculosis was evident in only one case. The differential diagnosis is also discussed. The diseases to be considered are mesenteric lymphadenitis due to Yersinia pseudotuberculosis or salmonella infection, and nonspecific mesenteric lymphadenitis.