NUT midline carcinoma.

NUT midline carcinoma (NMC) is a rare, aggressive human cancer, genetically defined by rearrangements of the gene NUT (HUGO symbol: C15orf55). In the majority (∼75%) of NMCs, most of the coding sequence of NUT on chromosome 15q14 is fused with BRD4 creating chimeric genes that encode BRD-NUT fusion proteins. In the remaining cases, NUT is fused to BRD3 or an unknown partner gene; these tumors are termed NUT-variant. Diagnosis of NMC is made by demonstration of expression of the NUT-fusion protein using a monoclonal antibody to NUT for immunohistochemistry, and confirmation of the fusion (BRD-NUT or NUT-variant) by fluorescent in situ hybridization or reverse transcriptase-polymerase chain reaction. BRD-NUT functions to block cellular differentiation and promote uncontrolled growth of carcinoma cells. Because the reagents and expertise required to diagnose NMC are not available in most laboratories, and because of incomplete awareness of this disease, NMC is frequently undiagnosed or misdiagnosed, and its actual prevalence is unknown. NUT midline carcinoma does not arise from any specific tissue type or organ. It presents as a poorly differentiated carcinoma originating from midline locations such as the head, neck or mediastinum. Although rare, NMCs occur throughout life, and advanced local disease is frequently accompanied by distant hematogenous metastases. There still is no effective treatment for NMC, there are no guidelines, and current approaches to treatment are based on discussions among a few oncologists who each have had a single experience treating this disease.