本文报道1例罕见的双表型鼻腔鼻窦肉瘤（biphenotypic sinonasal sarcoma, BSNS）患者，分析其临床病理特征。患者为35岁男性，因“反复右鼻涕中带血3月余”入院。行鼻内镜右侧鼻腔鼻窦颅底肿物切除术，术后病理活检。在光镜下观察，见肿瘤边界欠清晰，表面被覆纤毛柱状上皮细胞，局灶纤毛上皮细胞鳞状化生，黏膜内陷扩张及黏膜腺体增生。肿瘤由弥漫梭形细胞构成，细胞排列较密集，呈束状、编织状或人字形排列，细胞无明显异型性；染色质细腻，未见明显核分裂象和坏死；间质内见薄壁、扩张、分枝状的血管，呈鹿角样，未见明确横纹肌样分化区域。肿瘤组织的免疫表型为，Vimentin、H-Caldesmon、INI-1、Bcl-2和CD99呈阳性表达，Calponin、S100、MyoD1、SMA呈部分阳性表达，Ki-67增殖指数在热点区约为35%+；Myogenin、STAT6、SOX-10、Desmin、β-catenin、CK、CD34、NSE、PR和EMA均为阴性。基因检测显示，PAX-3基因断裂，FISH检测结果为阳性；SYT基因无断裂，FISH检测结果为阴性。该病例临床表现特征缺乏特异性，但被覆纤毛柱状上皮呈腺腔样结构，下陷于梭形细胞内呈囊性扩张，或梭形细胞内见增生的呼吸道腺体，是BSNS其相对典型的组织学特征。BSNS与其他梭型细胞肿瘤鉴别，应结合鼻腔鼻窦的发病部位、肿瘤由相对温和的梭形细胞构成、相对典型的组织学特征、表达肌源性和神经源性的免疫标记及特征性的PAX3基因检测进行综合诊断。

This study reported a rare case of biphenotypic sinonasal sarcoma (BSNS) and analyzed its clinicopathological features. The patient was a 35-year-old male admitted due to "recurrent right-sided nasal discharge mixed with blood for over three months". Endoscopic resection of a mass in the right nasal cavity, paranasal sinuses, and skull base was performed, followed by postoperative pathological biopsy. Under light microscopy, the tumor had an ill-defined boundary, with a surface covered by ciliated columnar epithelium. Focal squamous metaplasia of the ciliated epithelial cells was observed, along with mucosal invagination, dilation, and gland hyperplasia. The tumor was composed of diffusely distributed spindle cells densely arranged in bundles, woven, or herringbone patterns, without obvious cellular atypia. The chromatin was fine, and no obvious mitotic figures or necrosis were observed. In the stroma, thin-walled, dilated, and branched blood vessels resembling antlers were observed, and no definite regions of rhabdomyoblastic differentiation were identified. Immunophenotyping of the tumor tissue showed positive expression of Vimentin, H-Caldesmon, INI-1, Bcl-2, and CD99. Partial positive expression of Calponin, S100, MyoD1, and SMA. The Ki-67 index was approximately 35% in hotspot regions. Myogenin, STAT6, SOX-10, Desmin, β-catenin, CK, CD34, NSE, PR, and EMA were negative. Genetic testing showed PAX3 gene rearrangement, with positive FISH results. No rearrangement of the SYT gene was found, and the FISH result was negative. The clinical features of this case were nonspecific, but histologically, relatively typical features of BSNS were present, including gland-like structures formed by ciliated columnar epithelium invaginating into the spindle cell component with cystic dilation, or proliferative respiratory glands present within the spindle cell component. Differentiation of BSNS from other spindle cell tumors should be based on a comprehensive assessment of the site of origin in the nasal cavity and paranasal sinuses, the composition of relatively bland spindle cells, relatively typical histological features, expression of myogenic and neurogenic immunomarkers, and the characteristic PAX3 gene rearrangement.