Histologic long-term follow-up after embolization with polyvinyl alcohol particles.

A large facial vascular malformation was embolized with polyvinyl alcohol particles twice in 8 years. Resected tissue enabled long-term examination of this material, confirming its chemical inertness and revealing minimal tissue reaction to it apart from calcification. No particle migration, fragmentation, or absorption occurred. There was some recanalization of occluded vessels. Most vessels containing polyvinyl alcohol particles, and all of the larger vessels, were incompletely occluded, with particles becoming embedded in their walls.