The subrenal capsule assay in immunocompetent mice--the inevitable role of histopathology in assessment of this method as a tool determining tumor sensitivity to cytostatic drugs.

The subrenal capsule assay (SRC) in immunocompetent mice became one of commonly used approaches to evaluating the efficiency of cytostatic therapy. A comparison of the classical macroscopic evaluation according to the Bogden diagram with results of the histopathologic examination in 118 mice with implanted Yoshida sarcoma or human rectal adenocarcinoma demonstrated the tumor to be present to different extent only in 26 out of 50 macroscopically positive cases and, on the other hand, it was found in 3 out of 68 macroscopically negative animals. Histological changes in these cases, as well as a study of the dynamics of the development of histopathologic changes after tumor implantation and the changes after implantation of inert materials demonstrated that the resorptive and reparative granuloma, originating in immunocompetent mice under the renal capsule after implanting the tumor or other materials, simulates perfectly the growth of the tumor infiltrate. For this reason we consider this method in immunocompetent mice as unreliable when there is no parallel histological examination.