[en] Introduction and objective: Hemangyopericytoma are unfrequently malignant vascular tumours arising from Zimmerman?s pericytes (cells with mechanical support and vascular regulation rol). They account for about 1% of the tumours as a whole. Only about 20% arise in head and neck areas, mainly in the neck, sinonasal tract and skin. They are uncommonly encountered in the oral cavity or the pharynx. Their etiology reamains unclear. Case description: An unusual case report of an extending-to-canine-fossa malignant oral cavity hemangiopericytoma arising in the gingivolabial groove is provided. Neither its behaviour nor its anatomical origin are aknowledged to be the normal pattern of this disease. Discussion: Due to their unfrequency their differential diagnosis, mainly with other cystic tumours or conditions proper to this site, is not always available prior to surgical excision, which is the key for treatment. The presence of peritumoral tissue adherence and a bloody tumoral bedsite should lead to suspect this tumour. Their histological pattern of dendritic or staghorn appearance is very characteristic, although diagnosis relies in immunochemistry nowadays, with its characteristic intense positivity for vimentin and mild positivity for CD34.Surgery is key for treatment but should be complemented with chemotheraphy and/or radiotheraphy in high-grade tumours or when excision is not feasible or completely curative. Conclusions: The paucity of case reports by particular site and proliferative degree makes difficult to draw definitive conclusions on the management and treatment of this rare tumour difficult to suspect prior to surgery.

[es] Introducci?n y objetivo: Los hemangiopericitomas son tumores con origen vascular (pericitos de Zimmerman, c?lulas de soporte mec?nico con funci?n reguladora sobre la luz vascular) raramente malignos. Suponen un 1 % de todos los tumores y s?lo un 20% de todos ellos aparecen en cabeza y cuello, principalmente en cuello, piel y regi?n nasosinusal. Son excepcionales en faringe y cavidad oral. Su etiolog?a es desconocida. Descripci?n del caso: Presentamos un inusual caso de hemangiopericitoma maligno de cavidad oral a nivel del surco gingivolabial superior izquierdo extendido a fosa canina. Ni su comportamiento ni su localizaci?n anat?mica son los t?picos de esta entidad. Discusi?n: Dada su rareza, el diagn?stico diferencial de estos tumores no siempre puede realizarse con anterioridad a la excisi?n quir?rgica, debi?ndose realizar ?ste principalmente con otras enfermedades y tumoraciones qu?sticas propias de la zona. La presencia de adherencia a tejidos peritumorales y un lecho excesivamente sanguinolento pueden hacernos sospechar este tumor. Su patr?n histol?gico de aspecto dendr?tico o en asta de ciervo es muy caracter?stico, aunque actualmente el diagn?stico es inmunohistoqu?mico, siendo caracter?stica su intensa positividad a vimentina y positividades leves a CD34.La cirug?a, que es la base del tratamiento, debe complementarse con quimioterapia y/o radioterapia si el tumor es de alto grado, presenta factores de riesgo desfavorables o si la cirug?a no es factible o la resecci?n es incompleta.Conclusiones: La escasez de casos descritos por regi?n anat?mica particular y por grado proliferativo dificultan poder extraer conclusiones definitivas sobre el manejo y tratamiento de esta rara tumoraci?n dif?cil de sospechar antes de su estudio histol?gico.