[Histological and electron microscopy studies on the adenocarcinomatosis of laying hens].

Histological examination of 187 tumours from 98 hens (laying hybrids of various lines, age 80-123 weeks) showed that highly-differentiated tubulo-alveolar adenocarcinoma was present in 95% of the birds; in 20% it had a scirrhus structure. Histological and ultrastructural features of these carcinomas and their tendency to form secretory granules pointed to an origin from the protein-secreting part of the oviduct (magnum). In the remaining 5% of birds there were non-specific adenocarcinomas (probably ovarian carcinoma) and mesotheliomas.