Temporal and spatial factors in diethylstilbestrol-induced squamous metaplasia of the developing human prostate.

The effects of exogenous estrogen on the developing human prostate were examined in human fetal prostatic rudiments grown for 1 month as subcapsular renal grafts in athymic male nude mice treated with diethylstilbestrol (DES). Prostatic rudiments grown in untreated (control) hosts exhibited normal ductal morphogenesis, growth, and secretory cytodifferentiation. Squamous metaplasia was observed rarely in controls (2 of 22). Conversely, squamous metaplasia was observed in the prostatic utricle and urethra of all 17 specimens grown in DES-treated hosts. Proximal and distal prostatic ducts exhibited DES-induced squamous metaplasia in 13 and 12 of the specimens, respectively. When present, metaplastic changes were mild in the distal ducts. The distribution and intensity of metaplasia were related to the age of the specimen during the period of DES exposure. In specimens grown in DES-treated hosts to a gestational age equivalent of 16.5 weeks or less, squamous metaplasia was only seen in the prostatic utricle and urethra; however, in specimens grown to a gestational age equivalency of 17 weeks or more, squamous metaplasia was observed in the prostatic ducts as well. The nonuniform distribution of estrogen-induced squamous metaplasia within the developing prostatic ductal system emphasizes a regional and age-dependent susceptibility to exogenous estrogens in proximal ductal areas (near the urethra) as compared with distal ductal regions of the developing human prostate.