A Retrospective Analysis of Background Lesions and Tissue Accountability for Male Accessory Sex Organs in Fischer-344 Rats

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Abstract
Because the paired lobes (ventral, dorsal, lateral, and anterior) of the rat prostate have not been consistently sampled in many carcinogenicity and toxicity studies, comparison among different investigations has been compromised. The lack of specifi c site identifi cation for prostatic lesions further lessens the value of incidences reported. We present here the lobe-specific incidences and degree of severity of background prostatic, seminal vesicular, and ampullary glandular lesions in 1768 control Fischer-344 rats from 35 recent National Toxicology Program 2-year carcinogenicity and toxicity studies conducted in 4 laboratories. The dorsal and lateral lobes were combined and considered the dorsolateral lobe where inflammation, epithelial degeneration, mucinous cysts, and edema were observed. Infl ammation in the dorsolateral lobes was signifi cantly associated with pituitary gland adenoma whose prolactin was suggested to play an important role in pathogenesi s of prostatic inflammation. Epithelial degeneration, epithelial hyperplasia, infl ammation, edema, and adenoma were conspicuous in the ventral lobes. Infl ammation and edema occurred in the anterior lobes (coagulating glands). Inflammation, dilatation, epithelial hyperplasia, edema, and adenoma were observed in the seminal vesicles. Infl ammation was also present in the ampullary glands. We suggest an optimal embedment and trimming method in rat prostate and seminal vesicle to ensure adequate, consistent sampling.