MALIGNANT-LYMPHOMA SIMULATING LYMPH-NODE TOXOPLASMOSIS

On histological examination of 667 [human] cases originally suspected of lymph node toxoplasmosis, 12 cases were diagnosed as malignant lymphoma and 15 cases as atypical hyperplasia (AH) suspicious of malignant lymphoma. All 12 malignant cases were of Hodgkin''s disease: 8 lymphocyte predominant nodular type, 2 lymphocyte predominant diffuse type and 2 nodular scleroses. In all cases the lymph nodes contained small groups of epithelioid cells which were virtually indistinguishable from those seen in toxoplasmosis. In the differential diagnosis between lymph node toxoplasmosis and malignant lymphoma, the following features were helpful. In toxoplasmosis the general structure was preserved and germinal center were frequent in malignant lymphoma and in AH the general structure was destroyed. In some cases of toxoplasmosis germinal centers may be difficult to identify because their margins are indistinct due to clusters of epithelioid cells. In some types of Hodgkin''s disease and in some cases of AH with epithelioid cells, the general structure of the lymph node may be partially preserved. The occurrence of epithelioid cells within germinal centers seemed to be a specific feature for toxoplasmosis; it was never seen in malignant lymphoma or AH. The occurrence of strands of monocytoid cells was a fairly typical feature of toxoplasmosis but was also occasionally seen in Hodgkin''s disease or AH.