RESUMEN
Fortyone tumors were detected in a population of 1,649,003 cattle slaughtered in 4 abattoirs in Lombardy over a 5year period, for an overall prevalence of 2.5 tumors per 100,000 cattle. Tumors were classified according to the WHO histological classification of tumors of domestic animals. Alimentary and hemopoietic systems were commonly affected with 9 cases each. Other affected sites were the respiratory (n = 3), urinary (n = 2), endocrine (n = 2), musculoskeletal (n = 2), nervous (n = 1), and cardiovascular (n = 1) systems. The peritoneum was affected by 6 cases, while the primary location of 3 tumors of the connective tissues and 3 metastatic carcinomas was unidentified. Liver tumors and mesotheliomas, for which environmental risk factors are wellknown in humans, were common, as well as tumors typically encountered in pediatric human patients (tumors of mesenchymal tissues, pulmonary blastomas and nephroblastomas). These findings suggest the useful role of bovines as sentinel and model for human carcinogenesis. Our study indicates that the establishment of a bovine cancer registry in Lombardy is feasible considering its potential contribution to understanding the role of environmental risk factors in the genesis of tumors in animals and humans.