© 2020, Comenius University.AIM: Cornus mas L is commonly used due to its anti-inflammatory, anti-carcinogenic and anti-oxidant properties. In the study, the effects of C. mas L extract on a solid tumor were examined in the Ehrlich solid tumor model developed in Balb/C type mice. METHODS: Ehrlich acid tumor (EAT) cells (1x106 EAT cell) from the stock animal were injected subcutaneously (s.c.) through the nape of the mice. Treatment groups of solid tumor-induced animals received 100 mg/kg and 200 mg/kg of C. mas L extract intraperitoneally (i.p.) for 14 days. RESULTS: Tumor volumes and animal weights were found to be statistically significant compared to the control group (p < 0.05). AgNOR staining was performed in tumor tissues. Statistically significant differences were observed between the groups in terms of TAA/NA ratio (p < 0.05). Immunohistochemical and biochemical parameters were also evaluated. An estimation of tumor proliferation of the lung, liver, brain, kidney, testis and tumor antioxidant parameters viz. lipid peroxidation, reduced glutathione (GSH), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) was made. CONCLUSIONS: Our study showed that the anti-tumor effect of C. mas L in assisted tumor development with EAT cells, was mediated by the enhancement of oxidative stress with multiple mechanisms (Tab. 6, Fig. 12, Ref. 38). Text in PDF www.elis.sk.