Proliferative thrombovascular necrosis of the pinnae in a dog

The following are histopathological sections taken from the tips of the ear pinnae of a 5-year old male Labrador Retriever that presented with bilateral ulceration and necrosis of its ear tips. The dog is otherwise clinically well.

Fig 1. An H&E section of the ulcerated ear margin in which the arrows delineate the area of ulceration.
Fig 2. An H&E section showing a small thrombosed dermal artery. The smooth muscle wall is thickened and the lumen of the blood vessel is occluded by an organised thrombus (black arrow). The red arrows indicate the creation of new small blood vessels in attempt to bypass the thrombus, a process known as recanalisation.
Fig 3. An H&E section showing a normal dermal artery for comparison.

Final Diagnosis

Bilateral pinnal ulceration associated with chronic vascular thrombosis


Histopathological and clinical findings are consistent with the syndrome known as proliferative thrombovascular necrosis of the pinnae. This is a relatively uncommon syndrome whereby thrombosis and/or proliferative changes within the small dermal arterioles result in ischaemic necrosis of the ear tips. Both ears are typically affected, however unilateral lesions may occur. The cause is currently unknown. Surgical resection of the affected tissue provides the best chance for diagnosis and clinical cure.