In plant meristems, the balance of cell proliferation and differentiation is maintained by phytohormones, specifically auxin and cytokinin, as well as transcription factors. Changing of the cytokinin/auxin balance in plants may lead to developmental abnormalities, in particular, to the formation of tumors. The examples of spontaneous tumor formation in plants include tumors formed on the roots of radish (Raphanus sativus) inbred lines. Previously, it was found that the cytokinin/auxin ration is altered in radish tumors. In this study a detailed histological analysis of spontaneous radish spontaneous tumors was performed, revealing a possible mechanism of tumor formation, namely abnormal cambial activity. The analysis of cell proliferation patterns revealed meristematic foci in radish tumors. By using a fusion of an auxin-responsive promoter (DR5) and a reporter gene, the involvement of auxin in developmental processes in tumors was shown. In addition, the expression of the root meristem-specific WUSCHEL-relat