Idiopathic benign lichenoid keratosis on the pinna of the ear in four dogs

Histologically, multiple wart-like papules or hyperkeratotic plaques on the ear pinnae from 4 dogs were characterized as idiopathic benign lichenoid keratosis. Common histologic features included a discrete lesion of irregular and papillated epidermal hyperplasia with a moderate diffuse lichenoid interface inflammatory infiltrate consisting of lymphocytes and plasma cells. There was also focal hydropic degeneration of the epidermal basal cell layer, pigmentary incontinence, and mixed orthokeratotic and parakeratotic hyperkeratosis. In all 4 dogs, the pinnal lesions were unilateral and asymptomatic. Complete surgical excision was curative.