Malignant histiocytosis: a clinico-pathological study of 12 cases.

The clinico-pathological features of 12 cases of malignant histiocytosis (histiocytic medullary reticulosis), aged 12-60 years, were studied. Special emphasis was put on the analysis of the haematological, cytological and histopathological findings of the disease. Bone marrow aspirates and biopsies from involved tissues (liver, lymph node, spleen and skin) were found best suited for establishing the diagnosis. Cytochemical and ultrastructural data support the concept that the neoplastic cells belong to the mononuclear-phagocyte system. Three untreated patients died in less than 6 months. Median survival of the nine treated patients was 1 year. Seven patients were treated with the combination chemotherapy CHOP and four achieved a complete remission. Three of them are alive and continue in unmaintained remission for more than 1 year, surviving so far for 18+ to 31+ months. Two cases showed evidence of CNS involvement, one during life and the other as a post-mortem finding. The differential diagnosis from other related or unrelated disorders and the possible aetiological factors responsible for the disease are discussed in detail.