OBJECTIVE: To establish the mechanisms of pathomorphism of transplantable kidney cancer in rats that used flavonoid-containing hedge hyssop (Gratiola officinalis L.) extract in an in vivo experiments. MATERIAL AND METHODS: The experiment was carried out on 30 male Wistar rats with transplantable kidney cancer PA. At 72 hours after tumor inoculation, the rats in the experimental groups received hedge hyssop extract at an oral or intramuscular dose of 110 mg/kg/day for 12 days. A comparison group consisted of the animals with a tumor, but without exposure. The investigators used the immunohistochemical markers of apoptosis (p53, bax, bcl-2, Fas-receptor, Fas-ligand), autophagy (LC3B), proliferation (Ki-67), and angiogenesis (VEGF). During statistical data processing, the Shapiro-Wilk test was used to test the normality of the indicator distribution in the groups. Cramer-Welch's t-test was also employed to compare the groups. RESULTS: Histological examination of tumor tissue under the action of hedge hyssop extract showed the emergence of extensive areas of damage (necrosis and apoptotic bodies). With both routes of hedge hyssop extract administration, there was a sharp decrease in the expression of the proliferation markers Ki-67 and the angiogenesis marker VEGF and a high expression of the apoptosis markers p53, bax, CD95 (Fas/APO-1), and FAS-ligand in tumor cells and its absence in the comparison group. All the described changes were more pronounced with intramuscular administration. The expression of the autophagy marker LC3B increased with the oral administration of hedge hyssop extract and decreased with its intramuscular administration. CONCLUSION: A pronounced pathomorphism of kidney cancer develops due to consumption of hedge hyssop extract. This suppresses the proliferation, angiogenesis, and activation of apoptotic signaling and mitochondrial pathways and blocks protective autophagy. The autophagy marker LC3B can be used as an additional criterion for evaluating the therapeutic pathomorphism of tumors.