Primary mediastinal pure seminoma presenting with cervical lymphadenopathy and dyspnea in a young adult male: A Case Report

Background: Primary mediastinal seminoma is a rare extragonadal germ cell tumor accounting for a small proportion of mediastinal neoplasms. It predominantly affects young adult males and commonly arises within the anterior mediastinum. Because its clinical and radiological manifestations overlap with those of other mediastinal tumors, diagnosis may be challenging.
Case Presentation: We report the case of a 27-year-old man with no significant medical history who presented with progressive dyspnea, constitutional symptoms, and left cervical lymphadenopathy. Chest radiography demonstrated mediastinal widening, and contrast-enhanced computed tomography revealed a bulky anterior mediastinal mass measuring approximately 12.7 × 12 × 10.4 cm. Histopathological examination of a cervical lymph node biopsy demonstrated features consistent with pure seminoma. Immunohistochemistry showed strong positivity for CD117 and OCT3/4. Serum alpha-fetoprotein and beta-human chorionic gonadotropin levels were within normal ranges, and scrotal ultrasonography excluded a gonadal primary tumor. The patient received first-line cisplatin-based chemotherapy using the BEP regimen (bleomycin, etoposide, and cisplatin), resulting in significant tumor regression and clinical improvement.
Conclusion: Primary mediastinal seminoma should be considered in the differential diagnosis of anterior mediastinal masses in young men, particularly when associated with cervical lymphadenopathy. Histopathological confirmation with immunohistochemical characterization remains essential for diagnosis. Cisplatin-based chemotherapy continues to provide excellent outcomes, even in patients presenting with bulky disease.