[Hemangiopericytomas of the buccal cavity. Anatomoclinal and ultrastructural study. 9 cases]

Hemangiopericytoma, an unpredictable tumour, is not rare in the buccal cavity. Nine cases, most of which have been followed-up over a long period, show that, in this localisation, this neoplasm shows the unpredictable nature, though to a lesser degree (recurrences and metastases) of those situated in other parts of the body. Histological and ultrastructural analysis shows, apart from its characteristic perivascular features, much cellular polymorphism responsible for the diagnostic problems. A variety of cells, endothelial, fibroblastic and smooth muscle are observed next to the pericytes. The predominance of one or another cell type significantly affect the prognosis; immature forms with an endothelial predominance have a recurrent course, whilst fibrous forms have a much better prognosis. This diversity tends to support the histogenetic concept of one blastomatous cell responsible for the variable maturative possibilities.