Malignant histiocytosis simulating granulomatous disease.

In its clinical presentation, malignant histiocytosis may mimic infections or hematologic neoplasms, and pathologically it may be mistaken for Hodgkin's disease, histiocytic lymphoma, or viral lymphadenitis. The case histories of three patients in whom malignant histiocytosis clinically and pathologically simulated granulomatous diseases are reported. Erythrophagocytosis was not present in the initial bone marrow aspirates from two of the patients. One patient was considered to hve sarcoidosis or Wegener's granulomatosis; the second patient, Weber-Christian disease, and the third patient, a granulomatous disease of infectious origin. Granulomas have been found in tissues of patients who have Hodgkin's disease, but have been found only rarely in association with malignant histocytosis. An explanation for the presence of granulomas in association with malignant histiocytosis is offered: they may represent a phase in the evolution of the disease.