A Rare Case of NUT Carcinoma of the Thyroid.

NUT carcinoma is an aggressive, poorly differentiated squamous cell carcinoma, defined by rearrangement of the NUTM1 (Nuclear Protein in Testis) gene. Diagnosis is challenging due to histologic similarities with other poorly differentiated tumors requiring advanced diagnostic techniques. There is no established treatment, and prognosis remains extremely poor. A 27-year-old woman without known medical history presented with a rapidly enlarging neck mass and compressive symptoms. Chemotherapy for presumed squamous cell carcinoma with a component of anaplastic thyroid cancer based on pathology was initiated. Next-generation sequencing revealed thyroid NUT carcinoma with high PD-L1 expression, prompting PD-1 targeted therapy. The patient expired shortly afterwards from progressive disease. NUT carcinoma of thyroid origin is an extremely rare disease. This case brings awareness to the disease, highlights the importance of advanced diagnostic techniques and complexities in managing patients with NUT carcinoma.