Gizzard adenocarcinoma in an aged Humboldt penguin (Spheniscus humboldti)

Spontaneous gizzard adenocarcinoma was found in a 15-year-old male Humboldt penguin (Spheniscus humboldti). The lesser curvature of the gizzard wall was extensively and markedly thickened with a hard white tumour mass. Histopathologically, the tumour in the gizzard consisted of two structures: small to large acini lined by cuboidal or flattened cells with poor stroma in the mucosa, and undifferentiated tumour cells arranged singly or in cords with acinar structures separated by dense fibrous tissue in the muscular layer. Small white metastatic tumours of the intestine and the pancreas had a similar histological appearance to that in the muscular layer of the gizzard. From the location of tumour in the gizzard and the stainability with combined alcian blue pH 2.5-periodic acid Schiff, it was considered that this tumour might originate from the lining cells of the tip of the gizzard mucosal folds.