A rare, highly aggressive and lethal carcinoma that affects children and young adults. It arises from midline epithelial structures, most commonly the head, neck, and mediastinum. It is a poorly differentiated carcinoma and is characterized by mutations and rearrangement of the NUT gene. A balanced translocation t(15;19) is present that results in the creation of a fusion gene involving the NUT gene, most commonly BRD4-NUT fusion gene.