[Tumors of the gastrointestinal system in the rainbow trout]

Gastrointestinal tumours occurring in rainbow trout were investigated histologically and virologically. Neoplasms in stomach, medium and posterior intestine mainly in distal parts of these organs were found. Histologically the tumours are benign adenomatous polyps, differentiated adenocarcinomas, poorly differentiated adenocarcinomas, and poorly differentiated or entirely anaplastic adenocarcinomas. The last two types of tumours produced metastases into pancreas, pyloric caeca, and the liver. Virological investigations failed to confirm the presence of any oncoviral particles in these tumours. Aflatoxin analysis of fish foodstuffs gave negative results.