Airsac cystadenocarcinomas in cockatoos.

The clinical signs, radiographic and pathological findings of four histologically similar neoplasms that occurred as unilateral tumours projecting from the left axilla in three galahs (Eolophus roseicapillus) and one sulphur-crested cockatoo (Cacatua galerita) are described. In each case, the main reason for clinical presentation was respiratory distress. All cases were eventually fatal due to airway obstruction with evidence of extensive neoplastic invasion of the lungs, major airways and or humerus in all cases. A diagnosis of airsac cystadenocarcinoma was made in each bird on the basis of gross and histological appearance. The neoplasms were composed of fluid or air-filled sacs of proliferative cuboidal to squamous epithelial cells that stained positively with cytokeratin and negatively with vimentin. This was supported by a thin fibrovascular network although at least some areas in all four birds resembled airsac tissue. In some cases areas of haemorrhage, erythrophagocytosis, haemosiderosis and nodules of haemosiderophage infiltration with acicular cholesterol clefts were present in some parts of the sectioned tissue.