Naturally-occurring pulmonary tumors in rodents

The development of naturally-occurring lung tumors in rats, mice and Syrian hamsters is associated with aging. Rats and Syrian hamsters younger than 12 months rarely have this neoplasms, whereas in mice pulmonary tumors can be observed more frequently in animals of this age.The prevalence of spontaneous lung neoplasms is low in older rats and Syrian hamsters, but pulmonary tumors are quite frequent in a number of strains of mice. In rats and Syrian hamsters, little is known about the pathobiology of spontaneous lung tumors, in part because of their infrequent occurrence. In mice, more research on naturally-occurring lung neoplasms, particularly bronchiolo-alveolar tumors, has been done and immunohistochemical methods for the identification of cells of alveolar type II or Clara cell origin have been successfully applied