Vet Pathol 28:171-173 (1991) BRIEF COMMUNICATIONS and CASE REPORTS Focal Proliferative Eosinophilic Dermatitis of the External Ear Canal in Four Dogs

Dermatitides with marked tissue eosinophilia are com-monly occurring lesions in the cat, and two distinct entities are described: feline eosinophilic plaque characterized his-tologically by a hyperplastic superficial and deep perivascular to diffuse eosinophilic dermatitis with intraepidermal eosin-ophilic microabscesses, and feline eosinophilic granuloma, which is a granulomatous eosinophilic dermatitis with mul-tifocal flame figure^. ^ A similar granulomatous lesion occurs in hor~es.~ Eosinophilic granuloma has been reported in the dog as a rare lesion of the skin and oral Although it has been described in dogs of all ages, breeds, and sexes, dogs under 3 years of age, Siberian Huskies, and males appear to be at risk. The most common site of canine eosinophilic granuloma is the oral cavity, and the lesions are characterized by vegetative and ulcerated lingual or palatine masse~.~.~.~. l l Multiple cutaneous nodules and raised plaques on the ventral abdomen, prepuce, flanks, and limbs have also been report-ed.5.8Jo One case involved the nasal skin. ' The cutaneous lesions are non-pruritic and non-painful. Peripheral blood eosinophilia is occasionally observed. Although the blood and tissue eosinophilia and the response to corticosteroid therapy suggest that cutaneous hypersensitivity may be in-v o l ~ e d, ~ the cause of canine eosinophilic granuloma is still not clear. In this report, we describe an unusual location of focal, Fig. 1. Papillomatous mass from the external ear canal of a dog. There is a dense subepithelial inflammatory infiltrate and multifocal intraepithelial microabscesses. The epithelium is thickened and edematous. HE. Bar = 200 pm. Fig. 2. Focal area of densely eosinophilic collagen surrounded by eosinophils (flame figure) in dermis. HE. Bar = 100 pm