ABSTRACT
The self-cleaning function of the external ear canal is an effective means of regulating the ceruminous material and is highly important for aural health. In healthy dogs and cats, the normal external canal may contain yeasts, cocci, and keratinocytes. Malassezia dermatitis is a common contributing factor to the clinical signs of pinnal pruritus in dogs, less commonly in cats, suffering from atopic otitis or other concurrent dermatoses. Leishmania chagasi/infantum and Leishmania donovani are protozoal parasites that can cause severe disease in dogs. A variety of noninfectious conditions can cause inflammatory lesions on the pinna or periauricular region of cats and dogs. Plasma cell tumor is another round cell neoplasm that has a predilection for the pinnae in dogs. Sebaceous neoplasms may also be seen on the pinnae of dogs and, less frequently, cats. Ceruminous gland adenocarcinomas have multiple cellular criteria of malignancy in cytology samples including marked anisocytosis and anisokaryosis, coarse chromatin, large nuclei, macronucleoli, and binucleate and multinucleate cells.
