Abstract

Background: Mediastinal yolk sac tumor (YST) is a rare type of extragonadal germ cell tumor that typically occurs in young individuals. It is characterized by rapid progression, aggressive local invasion, and a significantly poorer prognosis compared with testicular germ cell tumors. The disease is often detected at an advanced stage, presenting as a large mediastinal mass causing compression of mediastinal structures and markedly elevated tumor markers, particularly alpha-fetoprotein (AFP). Case presentation: We report the case of a 43-year-old man, outside the typical age range for yolk sac tumor, who presented with hemoptysis, chest pain, and weight loss for one month. Clinical examination revealed superior vena cava syndrome with facial edema and collateral venous circulation over the neck and chest wall. Imaging studies demonstrated an isolated mediastinal lesion without evidence of tumors in other organs. The diagnosis required integration of clinical findings, imaging studies to exclude metastatic disease, serum tumor markers (markedly elevated AFP with normal β-HCG), histopathological findings (pleomorphic tumor cells arranged in glandular and microcystic patterns with Schiller–Duval-like bodies), and immunohistochemical staining showing SALL4 (+), CD117 (-), Glypican3 (+), AFP (+), cytokeratin (+), P63 (-), and LCA (-). These findings established the final diagnosis of primary mediastinal yolk sac tumor. Conclusion: Mediastinal yolk sac tumor is a rare but highly aggressive malignancy that predominantly occurs in young patients. Diagnosis of YST in older adults is challenging because of its rarity and atypical presentation. Accurate diagnosis requires a multidisciplinary approach integrating clinical findings, imaging, serum tumor markers, histopathology, and immunohistochemistry.