NUT Midline Carcinoma: An Underdiagnosed and Often Misunderstood Entity

NUT (nuclear protein in testis) midline carcinoma (NMC) is a rare and aggressive poorly differentiated squamous carcinoma that typically presents in midline regions, most often involving the mediastinum and head and neck. An entity previously thought to impact only pediatric and young-adult populations, NMC has been accepted more recently as impacting all ages. It is thought that NMC remains underdiagnosed, likely due to lack of awareness and the misconception of a pediatric-only presentation. Recent development of a NUT-specific monoclonal antibody has made confirming the diagnosis less problematic; however, this test is not widely available. Management of NMC is difficult, although recent developments in targeted therapeutics have shown promise. We present a case of presumed metastatic NUT midline carcinoma from our institution, as well as a review of NMC, focusing on clinical, histopathologic, and immunohistochemical features, and a brief discussion of the molecular aberrations characteristic of this entity.