High Prevalence of Caecal Dysplasia in Wistar/Furth Substrain Rats

Offspring of spontaneous colon tumor prone rats (WF/O) bred in our laboratory developed tumors in a very low incidence (less than 0.2 %), but about half of these rats had dysplastic epithelium with frequent erosion in the caecum. In nine animals (4.4%) submucosal glands of the caecum were observed. These dysplasia accompanied inflammatory cell reactions and regional lymph nodes were enlarged and packed with many plasma cells. Hybrid of WF/O rats and other inbred Long-Evans strain (LE) rats, having no dysplastic lesion of the caecum, had caecal dysplasia in a low incidence (10%). These data suggest that genetic factor(s) play an important role in the occurrence of caecal dysplasia in WF/O rats. These changes may be a precondition to the spontaneous occurrence of tumors in the proximal portion of the ascending colon with the aid of promoting factor(s).