Aim: The aim of this short communication was to describe a case of phyllodes tumor of the urinary bladder discovered in a female Fisher 344 rat that died during an experimental protocol to induce and study urothelial lesions by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN).
Methodology: From a group of several female rats exposed to BBN via drinking water over the course of 20 weeks, one animal died. At necropsy, a solid mass was identified in the urinary bladder lumen, with a diameter of 0.8 x 0.7 cm. This tumor was processed for histopathological examination and Feulgen coloration.
Results: Microscopically, the mass in the bladder was observed to be a phyllodes tumor. DNA content measured by image analysis of a Feulgen-stained section of the tumor and stroma cells displayed diploid DNA content in both components of the tumor.
Conclusion: This is the first reported phyllodes tumor in a rat's urinary bladder. The exact prognosis and histogenesis of phyllodes tumors of the urinary bladder remains to be determined by the accumulation of data from additional cases.