The article describes a clinical case of a patient aged 15 years with a sequential transformation of the ameloblastoma of the upper jaw into ameloblastic fibrosarcoma and undifferentiated round-cell sarcoma as a result of frequent relapses against the background of standard anticancer treatment. This clinical example is of interest not only because of the preservation of the mutation in the BRAF gene at all stages of transformation, which made it possible to conduct successful therapy with BRAF and MEK inhibitors after the exhaustion of all standard therapeutic possibilities.Conflict of interest. The authors declare no conflict of interest.Funding. The study was performed without external funding