目的·总结原发性纵隔卵黄囊瘤（yolk sac tumor，YST）的临床特征、影像学特征和诊治经验。方法·回顾性分析2016年9月—2023年5月上海交通大学医学院附属胸科医院收治的病理明确的原发性纵隔YST 29例。收集患者的临床资料、影像学检查结果、血清学报告、病理学报告、治疗方法等进行分析。结果·纯YST 22例，混合型YST 7例。男28例，女1例。平均发病年龄（24.5±5.9）岁。初始临床表现为胸闷（34.5%）、胸痛（27.8%）、咳嗽（34.5%）、咳痰（34.5%），以及无特异性症状（24.1%）等。胸部电子计算机断层扫描（computerized tomography，CT）增强显示29例病灶均位于前纵隔，最大径范围5.6~18.2 cm；形态不规则，密度不均匀，部分呈囊实性密度影，增强扫描可见不均匀强化；肿瘤边界不清，常压迫和累及周边组织。29例初诊患者中，28例血清学检测结果显示甲胎蛋白（alpha-fetoprotein，AFP）显著升高，另外1例未检测。29例患者中接受化学治疗（化疗）25例，手术治疗26例，放射治疗8例。确诊后直接手术者7例；经化疗后再手术治疗者19例，其中16例（84.2%）化疗后疗效评价为病灶缩小。手术后73.1%（19/26）的患者血清AFP有明显下降。化疗后56.0%（14/25）的患者血清AFP下降。结论·原发性纵隔YST好发于中青年男性，有一定临床和影像学特征表现，血清AFP升高，需要多学科综合治疗。

Objective ·To summarize the clinical features, imaging features, and diagnosis and treatment experience of primary mediastinal yolk sac tumor (YST). Methods ·Data of 29 patients with primary mediastinal YST, who attended Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine from September 2016 to May 2023, were collected and comprehensively analyzed, including imaging examination results, serum indicators, pathology reports and treatment methods. Results ·There were 22 cases of pure YST and 7 cases of mixed YST comprising 28 males and 1 female. The mean age of onset was (24.5±5.9) years. The initial symptoms were chest tightness (34.5%), chest pain (27.8%), cough (34.5%), expectoration (34.5%) and no specific symptoms (24.1%). Chest computerized tomography (CT) enhancement showed that all the 29 lesions were located in the anterior mediastinum. The maximum diameter of the lesions ranged from 5.6 cm to 18.2 cm. The lesions were irregular in shape, uneven in density, partially cystic and solid in density. The enhancement scan showed the solid part was slightly and moderately enhanced, and the low-density area was not enhanced. Tumor boundary was not clear because tumors often compressed and invaded surrounding tissues. Among the 29 newly diagnosed patients, serum alpha-fetoprotein (AFP) was significantly increased in 28 cases (1 case was not tested). Patients received multidisciplinary comprehensive treatment, including chemotherapy (25/29), surgery (26/29), and radiotherapy (8/29). Seven patients directly received surgery after diagnosis. Nineteen patients received chemotherapy first and then surgery; 16 (84.2%) cases were evaluated as lesion shrinkage after chemotherapy. After surgery, 73.1% (19/26) patients had a significant decrease in serum AFP. After chemotherapy, 56.0% (14/25) patients had decreased serum AFP. Conclusion ·Primary mediastinal YST usually occurs in middle-aged and young men, with certain clinical and radiographic features and elevated serum AFP, which requires multidisciplinary comprehensive treatment.