Clinical and imaging analyses of primary mediastinal yolk sac tumor

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.