An ultrastructural study of angiomatoid fibrous histiocytoma.

We studied the electron microscopy of two tumors which clinically and histologically conformed to what has been described as angiomatoid fibrous histiocytoma, a tumor thought to be of fibrohistiocytic origin. The ultrastructure of one tumor was that of a cellular angioma and the second tumor a vascular lesion with fibroblasts and histiocyte-like mononuclear cells. Our findings suggest that angiomatoid fibrous histiocytomas are basically vascular tumors with fibroblasts and other cells as secondary participants in some lesions. The behaviour of angiomatoid fibrous histiocytoma cannot be predicted from histology. Our findings of different ultrastructural components in histologically non-separable tumors lead to a question whether different ultrastructural composition is correlated with different biological behavior of these tumors. Further studies of similar cases are required if tumor morphology is to be correlated with clinical behavior.