[Hemangiopericytoma of the orofacial region].

Prognosis in 11 cases of hemangiopericytoma of the orofacial region (9 buccal and 2 parotid tumors) was, as with these lesions in other zones, an uncertain entity: 4 local recurrences within 8 months to 7 years; one fatal outcome after 3 years from pulmonary micrometastases. Histologic classification of these tumors into 3 cytologic groups of increasing malignancy (I to III) is a function of the number of their cytologic anomalies. They are also divided according to their overall morphology into poorly differentiated, differentiated and sclerous types. Positive correlations between structure and cytologic criteria of malignancy and structure and clinical course have been demonstrated. Ultrastructural examination in 2 cases showed polymorphic endothelial, fibroblastic and smooth muscle cells in contact with adult tumoral pericytes. This suggests the origin of the tumor from young cells of multiple potency rather than from adult pericytes.