This randomized controlled trial compares 6 versus 3 cycles of neoadjuvant chemotherapy in patients with potentially resectable locally advanced thymic epithelial tumors (TETs, WHO type AB/B/C, AJCC TNM stage IIIA-IVA). Patients are randomized 1:1 to receive either 6 or 3 cycles of chemotherapy (cisplatin + doxorubicin + cyclophosphamide for type B; nab-paclitaxel + carboplatin for type C thymoma/thymic carcinoma) every 3 weeks, followed by surgical resection when feasible. The primary endpoint is event-free survival (EFS). The study aims to determine whether extended neoadjuvant chemotherapy improves surgical outcomes and long-term survival in this rare malignancy.