Primary thyroid nuclear protein in testis carcinoma: a case report and literature review.

BACKGROUND: Nuclear protein in testis (NUT) carcinoma (NC) is a rare, highly aggressive neoplasm, usually accompanying with NUTM1 (NUT midline carcinoma family member 1) gene fusions. Primary thyroid NC is clinically rare and to date there is no established treatment guideline available for NC. We report a case of histopathologically confirmed thyroid NC and provide reference for diagnosis and treatment.

CASE DESCRIPTION: We presented a 32-year-old female admitted to hospital with "painful neck swelling and progressive dysphagia". Preoperative ultrasound-guided core needle aspiration biopsy suggested a poorly differentiated tumor. Considering the tumor was totally unresected on computed tomography (CT) scan, a partial thyroidectomy was performed to obtain sufficient tissue for a clear diagnosis. Histopathological specimens showed features of sudden keratosis. Strong immunoreactivity with NUT was detected by immunohistochemistry (IHC) and thus confirmed the diagnosis of NC. CK5/6, P40 and P63 were partially positive exclusively in keratosis area. Next-generation sequencing (NGS) and RNA sequencing results revealed a NSD3-NUTM1 fusion. The patient was treated with a combined regimen of radiotherapy of 70 Gy, chemotherapy with paclitaxel (albumin-bound), immunotherapy with nivolumab, targeted therapy with anlotinib and BET inhibitor NHWD-870, but the patient died 7 months after diagnosis.

CONCLUSIONS: Thyroid NC is a rare and distinct pathological subset of NUT carcinoma with a higher rate of NSD3-NUTM1 fusion. In the clinical diagnosis process, we recommended performing NUT IHC for poorly differentiated thyroid tumors. Gene rearrangement detection is also helpful for diagnosis and treatment. At present, surgery and radiation are still first choices for NC, and advances in targeted immunotherapy such as bromodomain and end motif inhibitors (BETi) may bring better treatment options to patients.