Background: The incidence of second malignancies seems to be a significant problem, increasing with the progress of oncology. The main factors causing the development of second neoplasms seem to
be chemotherapy and radiotherapy , but the endogenous factors that lead to the first and then second malignancy also play an important role. The most important therapeutic agent that causes second neoplasms is radiotherapy. It was applied in the treatment of almost all patients suffering from second neoplasms after the treatment of Wilms tumor. Second malignancies in the radiation field develop slowly - the average period of their incidence is 12 years.They are usually carcinomas, or bone and soft tissue sarcomas.Case Report: We present the case of a 16-year-old girl, who had undergone treatment of a Wilms tumor in childhood and developed second malignancy in the radiation field.The tumor proliferated in the hip bone infiltrating the vertebral column and inferior vena cava. Although the patient remained under oncological control, the second malignancy was diagnosed at an advanced clinical stage. Effective treatment was impossible because the tumor was inoperable and resistant to chemotherapy.Conclusions: Second malignancies are a rare, but very significant late effect of oncological treatment. Patients who were treated because of malignancies in childhood must be under oncologist’s control throughout the whole life. Patients after radiotherapy in the treatment of Wilms tumor require precise imaging studiesof bones situated in the radiation field.

Keywords: Wilms tumor second malinancy, Chondrosarcoma, children