Related Experiment Video
Updated: Mar 9, 2026
Thoracoscopic Extended Right Middle Plus Lower Sleeve Lobectomy for Non-Small-Cell Lung Cancer
Published on: February 27, 2026
Mediastinal seminoma associated with multilocular thymic cyst
Masato Inui1,2, Jun-Ichi Nitadori3, Shogo Tajima4
1Department of Thoracic Surgery, The University of Tokyo Graduate School of Medicine, Tokyo, Japan. minui-tky@umin.ac.jp.
Insights
A rare case of primary mediastinal seminoma with thymic cysts was successfully treated with surgery and chemotherapy. This finding highlights the importance of thorough diagnostic workups for anterior mediastinal masses.
Area of Science:
- Oncology
- Thoracic Surgery
- Pathology
Background:
- Anterior mediastinal masses can present diagnostic challenges, with thymoma and lymphoma being common considerations.
- Seminoma, a germ cell tumor, is typically found in the testes but can rarely occur in the mediastinum.
- Multilocular thymic cysts are benign lesions that can be associated with thymic neoplasms.
Purpose of the Study:
- To report a rare case of primary mediastinal seminoma coexisting with multilocular thymic cysts.
- To describe the diagnostic and therapeutic approach for this unusual presentation.
- To highlight the importance of comprehensive staging and adjuvant therapy.
Main Methods:
- Computed tomography (CT) and 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) scans for diagnosis and staging.
- Surgical resection via median sternotomy for tumor removal.
- Adjuvant chemotherapy with bleomycin, etoposide, and cisplatin (BEP) regimen.
Main Results:
- Pathological examination confirmed primary mediastinal seminoma with coexisting multilocular thymic cysts.
- Postoperative staging revealed no evidence of distant metastasis, except for an abnormal uptake in a mesenteric lymph node on FDG-PET.
- Adjuvant BEP chemotherapy resulted in complete resolution of the mesenteric lymph node uptake.
- No recurrence or metastasis observed during 16 months of follow-up.
Conclusions:
- Primary mediastinal seminoma can rarely present with coexisting thymic cysts, which may represent secondary changes.
- Multimodality treatment including surgery and adjuvant chemotherapy is effective in managing this rare condition.
- Close follow-up with imaging is crucial to monitor for recurrence or metastasis.
Abstract:
An asymptomatic 26-year-old man received an annual medical check-up, and chest X-ray showed a protrusion of the aortopulmonary window. Chest computed tomography (CT) revealed an anterior mediastinal tumor and cysts with thin wall and septum enhancement. The preoperative diagnosis was cystic thymoma or malignant lymphoma. We performed total resection of the tumor through a median sternotomy. The pathological findings revealed seminoma, positive for c-kit stain, and multilocular thymic cysts. Cysts were lined by normal squamous epithelium and no seminoma cells were located on their surface. So, cysts were probably secondary changes caused by seminoma cells themselves or inflammatory stimulations. No invasion to adjacent structures was seen. After the surgery, testicular ultrasound imaging and abdominal, pelvic, and cerebral CT showed no apparent tumor or enlarged lymph nodes; however, an abnormal uptake in the right mesenteric lymph node was pointed out by 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) scan. The patient received four courses of bleomycin, etoposide, and cisplatin (BEP) as adjuvant chemotherapy. Follow-up PET scan revealed no uptake in the right mesenteric lymph node. To date, no recurrence or metastasis has been identified for 16 months.
