FINE-STRUCTURAL STUDIES OF INDUCED-TUMORS ARISING WITHIN THE PROSTATIC COMPLEX OF LOBUND-WISTAR RATS

BACKGROUND. Morris Pollard, Phyllis Luckert, and colleagues have repor ted the occurrence of spontaneously arising tumors of the prostatic co mplex in aged Lobund-Wistar (L-W) rats, and have also shown that the g enesis of such tumors may be accelerated by means of intravenous admin istration of methylnitrosourea, followed by androgen supplementation. METHODS. Light and electron microscopic investigations of the tumors a rising under this regime were conducted, with the objective of documen ting morphological changes attending the transformation process; 10 tu mor samples were used for the electron microscopic studies. RESULTS. A ll tumors studied were adenocarcinomas arising within the prostatic co mplex of induced animals. These tumors varied in size, degree of diffe rentiation, and invasiveness. Foci of prostatic intraepithelial neopla sia were noted in light microscopic studies as well. Consistent fine s tructural features exhibited by cells of the induced adenocarcinomas i ncluded a large nuclear to cytoplasmic ratio; large irregular nuclei w ith heavily marginated chromatin; conspicuous nucleoli; abundant ribos omes and polysomes and a paucity of rough endoplasmic reticulum; and n umerous cytoplasmic vesicles and lipid inclusions. Numerous, short mic rovilli extended from the cell surface into a copious surrounding extr acellular matrix. CONCLUSIONS. Thus, these tumors shared many of the f ine structural features characteristic of the Dunning (rat) and human prostatic adenocarcinomas. (C) 1997 Wiley-Liss, Inc.