Distribution of Metastases in the Brown-Pearce Tumor. I. In Standard Breeds of Rabbits. ∗

Abstract

During studies on the transplantation of the Brown-Pearce tumor into the testicle of the rabbit, certain variations were noted between standard breeds of rabbits. 1 These variations included (a) the incidence and volume of the primary tumors, (b) the incidence, volume, and number of the metastases, and (c) the longevity and mortality of the animals after inoculation. All the animals were males, all received the same dosage into the testicle, all were in apparent good health, there was no significant variation in age between the breeds, and the diet and housing were uniform. The variations, moreover, wrere consistent and were most significant among breed samples inoculated at the same time. It was not possible, therefore, to explain the variations on the basis of sex, site of inoculation, physical condition, age, diet and housing, or season.

The results, extending (from a susceptibility of about 15% to a susceptibility of about 95%, seemed to be due to the inherent constitution of the pure breed strains used. The present paper reports efforts to determine whether the differences between the breeds were influenced by a selective liability of certain organs and tissues to metastatic involvement. For this purpose the protocols on 202 animals from 19 standard breeds were employed.

In each of the animals a detailed search for tumor foci was made in each of the 50 sites listed in Table I. A site containing one or more tumor nodules was designated as a single tumor focus. Forty-five animals were devoid of neoplastic growth at necropsy, 20 had primary tumors only, and 137 had metastases in one or more of the sites listed. Among the 137 animals with metastases there were 1,819 tumor foci, which amounts to approximately 20,000 tumor nodules.