Crusty thickening of the pinna. A: Right pinna of a squirrel showing gross irregular thickening and keratinised crusts. The other ear was similarly affected. B: Histological section of a similar case to that seen in Figure 2A. There is epidermal hyperplasia, hyperkeratosis with rete ridges extending into the dermis and keratin-filled cysts. On the right margin there is also an ulcerated trichoepithelioma (arrow). Haematoxylin and eosin stain, bar = 5 mm.