Comparison of experimental and spontaneous bladder urothelial hyperplasias occurring in BALB/c mice

Spontaneously occurring hyperplasia of urothelium of mice was compared morphologically to hyperplasia induced with 2-acetylaminofluorene (2-AAF) and 4-ethylsulfonylnaphthalene-1-sulfonamide (ENS). Simple and nodular hyperplasias were seen in all groups. Nodular downward hyperplasia was more commonly located in the vertex of the bladder of the 2-AAF treated mice but was more commonly located in the neck region of the ENS and control mice. The 2-AAF induced hyperplasia appeared to be capable of regression or progression to neoplasia. The ENS induced and the spontaneously occurring downward hyperplasia appeared to be secondary to a chronic cystitis and did not appear to progress to neoplasia.