RESUMEN
Recent molecular advances have identified a novel sarcoma defined molecularly by oncogenic fusion of the genes CIC and DUX4 termed CIC-DUX4 sarcomas. The most common site of involvement was the trunk but some cases have been described in the head and neck and extremities. We report one of the first cases of primitive renal CIC-DUX4 sarcoma: a 12-year-old boy who presented a renal tumor, a vena cava thrombus, and lung metastases. The morphological and immunohistochemical analysis showed an undifferentiated sarcoma. Molecular analysis demonstrated a CIC-DUX4 translocation, confirmed by fluorescence in situ hybridization. Despite treatment with chemotherapy, the evolution was unfavorable and the patient died 17 months after the diagnosis in a context of brain metastases. The diagnosis of sarcoma with CIC-DUX4 gene fusion is difficult in lack of specific pathological characteristics emphasizing the need for molecular analysis. Treatment has not yet been codified for these very aggressive tumors.