An Intriguing Case of Chemical Mimicry: Raised AFP Levels in NUT Carcinoma in Anterior Mediastinum

Nuclear protein of the testis (NUT) carcinoma (NC) is a rare and aggressive neoplasm that predominantly involves the thorax and the head and neck region. The hallmark of this neoplasm is its non-descript, poorly differentiated morphology, immunohistochemical mimicry and chemoresistance, leading to an almost invariably fatal outcome. A 47-year-old gentleman presented with a history of hoarseness of voice for one month, along with a recent development of shortness of breath. A CT scan showed the presence of mass in the anterior mediastinum with impending superior vena cava syndrome. Serum alpha-fetoprotein levels (AFP) and lactate dehydrogenase (LDH) were raised, done on clinical suspicion of a germ cell tumor. On morphology, the tumor showed a poorly differentiated phenotype with occasional foci resembling abrupt keratinization. Immunohistochemistry was positive for AE1/3,p40 and p63; however, markers for germ cell tumor, lymphoma, and small cell carcinoma were negative. The diagnosis of NC was clinched by NUT immunohistochemistry. NC presenting with raised AFP levels is an exceptional clinical scenario. To the best of our knowledge, this is the first case to be reported from India.