NEUROENDOCRINE DIFFERENTIATION OF PAPILLOMAVIRUS-ASSOCIATED TUMOURS AND TUMOUR-LIKE LESIONS OF THE URINARY BLADDER IN CATTLE

Twenty-eight urothelial tumours of the urinary bladder were studied in 4-16-year-old cattle grazing on lands rich in bracken fern. Four primary adenocarcinomas, twelve papillary carcinomas, ten invasive carcinomas, two urothelial carcinomas with endophytic growth were examined. They were classified using morphological parameters which have been recently suggested in the report on the new histological classification of urothelial tumours of the urinary bladder of cattle. Furthermore, some incidental benign reactive processes such as cystitis glandularis and intestinal metaplasia, coexisting with urothelial tumours, were also investigated. E5 oncoprotein of bovine papillomavirus type 2 (BPV-2) was detected by immunoprecipitation in twenty-two tumours (79%). The remaining six tumours (21%) were E5-negative. Neuroendocrine differentiation was evident in fifteen tumours, four adenocarcinomas and eleven urothelial tumours; twelve of them, that is 80% (four adenocarcinomas and eight urothelial cancers) were E5-positive. Primary adenocarcinomas were composed of a number of multiple glands embedded in a loose stroma. Glandular lumina were lined by tall columnar cells which showed a marked immunoreactivity to chromogranin A, synaptophysin and serotonin. In eight papillary carcinomas containing varying degrees of a glandular or glandular-like differentiation, immunoreactivity was focally scattered among glandular structures. Two of them were E5-negative. Finally, immunoreactivity was also present in three invasive urothelial carcinomas. They were composed of glandular-like structures, cords and nests of neoplastic cells. Glandular-like structures showed a more marked immunoreactivity. A weak immunoreactivity was also seen in the cells at the edges of the nests. One of them appeared to be E5-negative. This study widens the spectrum of histological neoplastic urothelial lesions of cattle and affords further evidence that microscopic patterns of bovine urinary bladder tumours share striking morphological similarities with the human counterparts.