P2.04-004 Thymectomy without Definitive Diagnosis Could Be Feasible in Patients with Suspicious of Thymic Epithelial Tumor: Topic: Thymic Malignancies Clinical and Translational

Abstract

As for thymic epithelial tumors (TETs), National Comprehensive Cancer Network guideline has suggested that complete excision of tumor should be performed without preoperative biopsy when resectable. However, there have been very few evidences on this strategy of diagnosis and treatment. The purpose of this study is to evaluate the validity of radical resection of anterior mediastinal masses (AMMs) without pathological confirmation. Two hundred and fifty-eight patients with AMMs underwent surgical resection between 2004 and 2015 at the Nagoya University Hospital. Among them, 186 patients were suspected to have TETs by clinical features, serum tumor markers, and the findings of computed tomography (CT) and positron emission tomography (PET). We retrospectively reviewed cases of the patients with AMMs and evaluated the strategy of treatment for them. Of the186 patients with suspicious of TETs, 56 patients received preoperative biopsy and had the pathological diagnosis. The method included CT-guided needle biopsy in 49 patients (26%) and video-associated thoracic surgery biopsy in 4 (2%) to plan neoadjuvant therapy and/or to distinguish from malignant lymphomas or malignant germ cell tumors, and intraoperative pathologic examination using frozen section of the tumor in 3 (1.6%). The remaining 130 patients (70%) underwent thymectomy without pathological confirmation. Among them, the tumors in 115 patients (88%) were finally diagnosed as TETs including 100 thymomas, 11 thymic carcinomas and 4 thymic carcinoids. The patients except one received complete resection. The remaining 15 patients (12%) were diagnosed as 4 thymic cysts, 4 lymphomas of mucosa-associated lymphoid tissue type (MALT), 2 bronchogenic cysts, 2 mature teratomas and 3 other tumors. Thymic cysts with thick wall in part and small MALT lymphomas with intermediate accumulation of PET were sometimes difficult to distinguish from TETs preoperatively. Eighty-eight percent of the patients with suspicious of TETs who underwent thymectomy without biopsy were accurately diagnosed and properly treated with complete resection. Thymectomy without a definitive diagnosis could be feasible in patients with suspicious of TETs when they are considered resectable, although there are some tumors such as thymic cyst and MALT lymphoma hard to distinguish from TETs.