NUT carcinoma of the parotid gland:a cinicopathological analysis of one case and review of literature

LIN Ze-yang; LIAO Hong-feng; GUO Shu-jing; CHEN Chun-cheng; BAI Ting-ting; YE Yu-han; LIU Zheng-jin

doi:10.3969/j.issn.1007-8096.2025.04.017

Abstract：Objective: To investigate the clinical pathological features, immunophenotype, molecular genetic characteristics, differential diagnosis, and prognosis of parotid NUT carcinoma. Methods: A case of parotid NUT carcinoma was collected, and immunohistochemistry (EnVision two-step method) and fluorescence in situ hybridization (FISH) were used to label tumor cells, analyzing its histomorphological features and prognosis. Related literature was reviewed. Results: The patient was a female aged 18 years, with a tumor located in the left parotid gland, with a maximum diameter of 3.2 cm. Microscopically, the tumor tissue was arranged in sheets, nests, and strands. The cells were small, with relatively uniform nuclei, coarse chromatin, and prominent nucleoli. The cytoplasm was eosinophilic or amphophilic, showing plasmacytoid or rhabdomyoblastic changes. Focal keratinization or squamous epithelial metaplasia was observed. Necrosis and mitotic figures were common. Immunophenotype: Tumor cells were positive for NUT, CK-pan, p63, MYC, p40, EMA, INI-1, and BRG1, while negative for CD117, CD99, WT-1, SYN, CgA, CD56, and S-100. Ki-67 proliferation index was 40%. NUTM1 rearrangement was positive. The patient died 6 months after follow-up. Reviewing domestic and foreign reports of parotid NUT carcinoma, a total of 15 cases were reported. Combined with this case, a total of 16 cases were analyzed. Parotid NUT carcinoma mainly occurs in young people (12–55 years old), with an average age of 30.4 years and a median age of 32–34 years. It is more common in males, with a male-to-female ratio of 1.7:1. The incidence in left and right parotid glands is similar, with a ratio of 1.3:1. Tumor size ranges from 1.5 cm to 9 cm, with an average of 3.7 cm. Patients have a very poor prognosis, with 80% of cases developing lymph node metastasis; 50% of cases developing distant metastasis; survival time varies from 2 months to more than 2 years, with a median survival time of only 7 months. Grossly, all tumors showed infiltrative growth. Microscopically, 93.3% of tumor tissues showed local squamous epithelial differentiation or keratinization, with one case showing cartilage differentiation. Immunophenotypically, all cases expressed p63 and NUT. FISH detected NUTM1 rearrangement in all cases, and 77.8% of cases had BRD4 as the partner gene. Conclusion: Parotid NUT carcinoma is very rare, mostly occurring in young people. Diagnosis and differential diagnosis rely on morphological changes combined with immunohistochemistry and fluorescence in situ hybridization. Treatment primarily involves surgery combined with radiotherapy and chemotherapy, but the clinical prognosis is extremely poor.