Objective: The purpose of the study was to explore the usefulness of fluorine-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET-CT) in the preoperative assessment of isolated anterior mediastinal lesions, especially in the planning of operative strategy (biopsy or upfront resection).
Methods: During the last 36 months, 19 consecutive patients (10 males, mean age 54+/-16 years) underwent PET-CT in the preoperative work-up of isolated anterior mediastinal diseases. Maximal transverse diameter at CT and the postoperative histology and Masaoka staging for thymomas were collected and related to the maximum standardised uptake values (SUVs). Thymomas were divided into low-risk thymoma (LRT=A, AB and B1) and high-risk thymoma (HRT=B2, B3 and C).
Results: There were 13 thymomas (six LRT and seven HRT), three lymphomas and three other primitive thymic tumours (one paraganglioma, two non-seminomatous germ cell tumours). In LRT, the mean SUV was 3.3+/-0.5 resulting significantly lower than HRT, 13.5+/-7 (p=0.009). The SUV in LRT was also significantly lower with respect to lymphoma, 12.4+/-4 (p=0.001), and the other primitive anterior mediastinal tumours, 8+/-0.8 (p=0.001). Between thymomas we found a significant correlation between Masaoka stage and SUV, r=0.718, p=0.006. No correlation was found between transverse diameters and SUV, r=0.141, p=0.6.
Conclusions: In our experience, low SUV (<5) is associated with LRT and minimal invasive thymoma (Masaoka stages I-II) and, therefore, susceptible to upfront surgery. For lesions with an infiltrative aspect on CT scan associated with a higher SUV (>5), an open biopsy is mandatory to exclude mediastinal lymphomas or, in case of HRT, to address a neoadjuvant treatment.