[Contribution to morphology of malignant histiocytosis (author's transl)].

9 cases of malignant histiocytosis (3 males, 6 females, age 30 to 83 years) have been observed in the biopsy and autopsy material of the Institute of General Pathology and Pathological Anatomy of the Medical Academy of Erfurt, GDR. Malignant histiocytosis which derives from tissue macrophages/histiocytes is characterized by a proliferation of non-cohesive atypical histiocytes mainly in lymph nodes, spleen, liver, and bone marrow. The tumor cells are large, pleomorphic and show an irregularly-shaped, cleaved and often kidney-like nucleus with 1-3 medium-sized nucleoli. The cytoplasm is moderately basophilic and grey-blue when stained with azure B eosin or according to Pappenheim. Diffuse cytoplasmic activities of nonspecific esterase and acid phosphatase are further properties. Another sign of malignant histiocytic cells should be stressed, i.e., the diffuse intracytoplasmic perinuclear PAS-positive spot which hitherto has not been mentioned in the literature. Morphological variants of malignant histiocytosis are fibrosing (2 cases) and erythrophagocytosing types (2 cases). Reactive histiocytosis, histiocytosis X and malignant non Hodgkin-lymphomas, esp. immunoblastic lymphomas, are to be taken into account in differential diagnosis.