Very late recurrence of thymoma after 14 years: an International Thymic Malignancy Interest Group Tumor Board case report from a Turkish multidisciplinary team.

Background: Thymomas are generally slow-growing tumors with a favorable prognosis; however, late recurrences have been well documented in the literature and may occur many years after complete (R0) resection. In this report, the multimodal management of a patient who experienced recurrence 14 years after surgery is presented as discussed during the multidisciplinary International Thymic Malignancy Interest Group (ITMIG) Tumor Board meeting on 17 October 2025. Case Description: An 18-year-old female patient underwent median sternotomy in 2006 for resection of a 15.5-cm type B1 thymoma. Histopathological examination revealed microscopic transcapsular invasion with negative surgical margins, and adjuvant therapy was not recommended at that time. In 2020, progressive myasthenic symptoms led to re-evaluation, and imaging demonstrated multifocal right pleural recurrence with suspected involvement of the inferior vena cava and hepatic interface. Fine-needle aspiration biopsy confirmed recurrent World Health Organization (WHO) type B1 thymoma. Because complete resection was considered unlikely, the patient received cisplatin/etoposide chemotherapy followed by definitive chemoradiotherapy, achieving major radiologic response and disease stability. In 2024, after progression of a paravertebral recurrent lesion, salvage surgery was performed via right thoracotomy, including wedge resection, pleurectomy, mediastinal lymph node dissection, and intraoperative hyperthermic intrathoracic chemotherapy. The patient has since remained disease-free on continued surveillance. Conclusions: In thymic epithelial tumors with increased risk of recurrence, multimodal treatment strategies may improve long-term outcomes. This case highlights that very late recurrence may occur even after R0 resection and supports lifelong surveillance. Long-term follow-up should include periodic contrast-enhanced thoracic computed tomography, with magnetic resonance imaging considered in younger patients to reduce cumulative radiation exposure.