Arteriovenous haemangioma in two dogs and a cat.

Haemangiomas are benign vascular tumours and several types can be distinguished based on microscopical features. Capillary and cavernous haemangiomas are most commonly reported in man and domestic animals. Arteriovenous haemangiomas are rare variants in man and herein we describe this subtype in two dogs and one cat. One dog and the cat presented with a cutaneous vascular lesion, the other dog with a bleeding mass in the tongue. Surgically excised masses comprised non-encapsulated proliferations of variably sized arterial- and venous-like vessels, accompanied by clusters of capillaries and immature vascular structures in the feline cutaneous tumour and the canine lingual neoplasm. All vasoformative elements had von Willebrand factor-positive endothelia enclosed by a smooth muscle actin-positive tunica media or by pericytes. The results of this study expand the range of differential diagnoses for vascular neoplasms in the dog and cat.