NUT Carcinoma: A Diagnostically Challenging Rare Entity with an Aggressive Course: A Case Series

Nuclear Protein in Testis (NUT) carcinomas are rare, extremely aggressive, poorly differentiated squamous carcinoma, characterised by the presence of NUT gene (NUTM1) rearrangement. NUT carcinoma most commonly arises in head and neck region and thorax however, they can occur in other parts of the body also. Here, we are presenting a case series of three cases of NUT carcinoma. All patients were females with disease involving head and neck region. The first case was an eight-year-old girl. The second case was a 36-year-old woman. The third case was a 61-year-old woman. Histopathology of all cases showed poorly differentiated neoplasm, comprising of sheets of monotonous cells with minimal indistinct, clear cytoplasm, round to oval nuclei with prominent nucleoli. High mitotic rate with areas of tumour necrosis were also present. Areas of abrupt keratinisation classically described in this entity were seen in two of the cases. Speckled nuclear positivity for NUT1 monoclonal antibody by immunohistochemistry, which is sensitive and specific for diagnosis was observed in all three cases. There is no definite treatment for this disease, and most patients respond poorly to conventional chemotherapy and radiation. Targeted therapy targeting the BRD4 portion of BRD4-NUT, termed BET bromodomain inhibitors, are in clinical trials. Two of our patients succumbed to disease within one year of diagnosis. Third patient is on follow-up for eleven months after diagnosis.