Role of fluorine-18-fluorodeoxyglucose positron emission tomography in selecting candidates for a minimally invasive approach for thymic epithelial tumour resection.

Objectives: We evaluated the potential of preoperative fluorine-18-fluorodeoxyglucose positron emission tomography to predict invasive thymic epithelial tumours in patients with computed tomography-defined clinical stage I thymic epithelial tumours ≤5 cm in size who are generally considered to be candidates for minimally invasive approaches.

Methods: From January 2012 to July 2022, we retrospectively analysed patients who exhibited tumour-node-metastasis (TNM) clinical stage I thymic epithelial tumours with lesion sizes ≤5 cm as determined by computed tomography. All patients underwent fluorine-18-fluorodeoxyglucose positron emission tomography preoperatively. We analysed the association of maximum standardized uptake values with both the World Health Organization histological classification and the TNM staging classification.

Results: A total of 107 patients with thymic epithelial tumours (thymomas, 91; thymic carcinomas, 14; carcinoids, 2) were evaluated. Nine patients (8.4%) were pathologically upstaged: TNM pathological stage II in 3 (2.8%), III in 4 (3.7%) and IV in 2 (1.9%). Among these 9 upstaged patients, 5 had thymic carcinoma with stage III/IV, 3 had type B2/B3 thymoma with stage II/III and 1 had type B1 thymoma with stage II. Maximum standardized uptake values were a predictive factor that distinguished pathological stage >I thymic epithelial tumours from pathological stage I [best cut-off value, 4.2; area under the curve = 0.820] and thymic carcinomas from other thymic tumours (best cut-off value, 4.5; area under the curve = 0.882).

Conclusions: Thoracic surgeons should carefully determine the surgical approach for high fluorodeoxyglucose-uptake thymic epithelial tumours and keep in mind the issues associated with thymic carcinoma and potential combined resections of neighbouring structures.