Bacterial lymphadenitis with the picture of a lymphoepithelioid cell lymphoma--Lennert's lymphoma.

Three cases with the typical light microscopic picture of lymphoepithelioid cell lymphoma (so-called Lennert's lymphoma) were investigated by electron microscopy. Surprisingly, Lennert's lymphoma could be excluded in two cases. These two cases exhibited, in addition to pleomorphic lymphocytes and epithelioid cells, macrophages with accumulations of bacteria, indicating that a bacterial infection was the cause of the disease. By comparing the typical case of Lennert's lymphoma with the other cases, we found several criteria for distinguishing between Lennert's lymphoma and bacterial lymphadenitis. In bacterial lymphadenitis: (1) small and medium-sized lymphocytes exhibited a wide cytological spectrum whereas the lymphocytes in Lennert's lymphoma were relatively uniform; the lymphocytes with prominent lysosome-like granules found in Lennert's lymphoma were not seen; (2) cytology and distribution of epithelioid cells were similar to those in Lennert's lymphoma; (3) epithelioid venules contained recirculating lymphocytes, which were rarely found in Lennert's lymphoma; (4) numerous interdigitating reticulum cells, fibroblasts and myofibroblasts were seen, but not in Lennert's lymphoma; (5) focal increase in reticulin fibres was the main difference in light microscopy; (6) rod-shaped bacteria were accumulated in the cytoplasm of a few macrophages. The presence of bacteria could not be demonstrated unequivocally by light microscopy. In both cases the large number of intracytoplasmic bacteria suggests that this unusual and until now unknown lymphadenitis is the result of an infection caused by facultative intracellular parasitic bacteria. The outcome of bacterial lymphadenitis that gives the false impression of Lennert's lymphoma is uncertain. Cure was achieved in one of our cases. The other patient died before therapy was commenced.