Primary mediastinal seminoma with chronic granulomatous inflammation and lymphoid follicular hyperplasia: A case report and literature review

Background: In this paper, a 22-year-old male patient with primary mediastinal seminoma (PMS), a rare extragonadal germ cell tumor, was described. Due to chest pain, this patient was admitted to the hospital and received the thoracic contrast-enhanced CT and further magnetic resonance imaging (MRI) examination, with the result of a mass in the anterior mediastinum, which indicated a benign tumor or tumor-like lesion such as thymic or thymomas. After the testicular metastasis was excluded after surgery, he was pathologically diagnosed with PMS, accompanied by secondary histological features, including a dense inflammatory infiltrate comprising a combination of lymphocytes and granulomatous inflammation that may obscure the underlying neoplasm, thus leading to missed diagnosis or misdiagnosis or delayed diagnosis. Therefore, a proper understanding of the histological features and rare accompanying features of this disease is essential for the correct diagnosis and postoperative treatment.