| Abstract: | ![]()
Light and electron microscopical, immunohistochemical and clinical characteristics in 42 cases of malignant neoplasms, arising from true histiocytes, are described. These were separated in a lymphoma-like subtype, called true histiocytic lymphoma (29 patients) and a disseminated variant, called malignant histiocytosis (9 patients). In addition 4 related histiocytic tumors are discussed, including 2 tumors arising from interdigitating cells. Sinus pattern and cytologic features, especially 'window' nuclei, are emphasized as diagnostic criteria. Erythrophagocytosis was not a constant finding. Electron microscopic features, presence of acid phosphatase, acid alpha-naphthylacetate esterase, lysozyme, alpha 1-antitrypsin, alpha 1-antichymotrypsin, Ia-antigen and absence of B- and T-cell markers, were important in establishing the histiocytic nature or excluding a non-histiocytic tumor. A distinct male predominance existed (male:female = 2.5:1) with a higher relapse free period in females (p = 0.032). A high number of mitotic figures appeared to be a favourable sign, p = 0.020 and 0.019, for remission rate and relapse free period respectively. The degree of cell differentiation and the immunohistochemical pattern did not show a correlation with remission and relapse free period. Extranodal involvement and the presence of short profiles of endoplasmic reticulum were prognostically unfavourable signs. True histiocytic lymphomas showed a higher remission rate (p = 0.041) and relapse-free period (p = 0.017) than malignant histiocytosis. |
