MOUSE UTERINE-TUMORS RESEMBLING MALIGNANT FIBROUS HISTIOCYTOMA - LIGHT AND ELECTRON-MICROSCOPIC STUDY

Seven uterine tumours induced in CBA mice by 1.2-dimethylhydrazine are described. Tumours were of a large size. weight of 1.5-4 g/O and cons isted of fibroblast-like, histiocyte-like and undifferentiated cells w ith high mitotic index. Several growth patterns were distinguished: wh irl-like pleomorphic, fascicular, myxoid and hemangiopericytomatous. E ach tumour had at least two growth patterns, one of them being predomi nant. All the tumours contained giant cells of variable structure: ben ign looking and bizarre. PAS-positive diastase-resistant cytoplasmic g ranules were found in 5 tumours. Erythrophagocytes were observed. Meta stasis to the forestomach was found in one case; lungs, liver and othe r inner organs were intact. Ultrastructurally undifferentiated cells w ith scarce organelles, fibroblast-like cells and histiocyte-like cells with indented nuclei and numerous lysosomes were found. The described uterine tumours are morphologically similar to malignant fibrous hist iocytomas of men and rats.