RESUMEN
NUT-midline carcinoma is a rare and very aggressive tumor, with fast progression and poor prognosis. It should be suspected in poorly differentiated tumors, especially if located in midline structures of the head, neck, and thorax. It is characterized by gene translocation of nuclear protein in testis (NUT) gene from chromosome 15, most frequently to bromodomain containing protein 4 (BDR4) gene on chromosome 19. We present a case of mediastinal NUT-midline carcinoma in 11-year old boy.CT revealed a large mediastinal mass on the right side, with elevated serum alpha-fetoprotein (AFP), neuron-specic enolase (NSE), ferritin and lactate dehydrogenase (LDH). The patient was treated with chemotherapy, but the progression of disease was rapid, and he died within four months after the onset of disease.