ULTRASTRUCTURAL BASIS FOR THE HEMATOGENOUS METASTATIC PROCESS IN A MALIGNANT FIBROUS HISTIOCYTOMA

The electron microscopic examination of a biopsy from a malignant fibr ous histiocytoma showed the existence of two different types of capill aries. Those from the invaded muscle tissue exhibited abnormal endothe lial cells, widened basement membranes and occluded lumens. Tumor cell s observed beside them were not seen penetrating capillary walls. Capi llaries located into the turner mass showed vacuolated endothelial cel ls and pericytes, and widened and clearly laminated basement membranes , Capillary lumen was not occluded. In many cases capillary channels w ere formed only by basement membrane, Tumor cells were seen invading c apillary walls and inside capillary lumen, This study provides the his to-pathological basis for the hematogenous metastatic process in a mal ignant fibrous histiocytoma.