Early manifestations of induced prostate tumors in Lobund-Wistar rats.

Lobund-Wistar (L-W) rats are susceptible to spontaneous and induced metastasizing prostate cancer. In the search for the initial site of tumor development in the induced disease, rats at risk were examined periodically to acquire this information. In the course of 12 months after the onset of the induction of prostate cancer in L-W rats, 14 of 40 rats (35%) developed visible tumors in the anterior and in the dorso-lateral lobes of the gland. The prostate tumors appeared at 7 months and thereafter. Two of the tumor-bearing rats had developed, in addition, a visible neoplasm in the seminal vesicle. None of the rats with small early tumors had developed visible metastatic tumors, which were manifested in rats with large tumors.