Pathological study of naturally occurring adenocarcinomas demonstrating differentiation in ducks

Case 1, a mucinous adenocarcinoma, was in the pancreas of a 5-year-old male mandarin duck. The tumour comprised a single layer of duct-like structures with abundant fibrous stroma. The neoplastic cells produced a large amount of mucin, and dense or moderately dense mucin granules were observed ultrastructurally. Case 2 was a 1-year-old male mandarin duck, which had a type II pneumocytoid carcinoma within the thoracic air sacs. Light microscopy revealed papillary growths composed of stratified neoplastic epithelium. At the ultrastructural level, the tumour cells had osmiophilic lamellar granules in the cytoplasm. Case 3, a ciliated cell adenocarcinoma with squamous metaplasia, was detected in the right lung of a 2-year-old male domestic duck (Anas platyrhynchos forma domestica). The neoplasm consisted of tubular structures with areas of squamous differentiation in places. The presence of cilia was confirmed by electron microscopy. The three adenocarcinomas appeared high-grade or moderate-grade malignant tumours in some aspects, but showed granules or cilia that are suggestive of their origin. The presence of cells retaining the capacity for differentiating into well-differentiated cells may be characteristic of sporadically occurring avian adenocarcinomas.