Fine structural studies of induced tumors arising within the prostatic complex of Lobund-Wistar rats.

Background: Morris Pollard, Phyllis Luckert, and colleagues have reported the occurrence of spontaneously arising tumors of the prostatic complex in aged Lobund-Wistar (L-W) rats, and have also shown that the genesis of such tumors may be accelerated by means of intravenous administration of methylnitrosourea, followed by androgen supplementation.

Methods: Light and electron microscopic investigations of the tumors arising under this regime were conducted, with the objective of documenting morphological changes attending the transformation process; 10 tumor samples were used for the electron microscopic studies.

Results: All tumors studied were adenocarcinomas arising within the prostatic complex of induced animals. These tumors varied in size, degree of differentiation, and invasiveness. Foci of prostatic intraepithelial neoplasia were noted in light microscopic studies as well. Consistent fine structural features exhibited by cells of the induced adenocarcinomas included a large nuclear to cytoplasmic ratio; large irregular nuclei with heavily marginated chromatin; conspicuous nucleoli; abundant ribosomes and polysomes and a paucity of rough endoplasmic reticulum; and numerous cytoplasmic vesicles and lipid inclusions. Numerous, short microvilli extended from the cell surface into a copious surrounding extracellular matrix.

Conclusions: Thus, these tumors shared many of the fine structural features characteristic of the Dunning (rat) and human prostatic adenocarcinomas.