Search

Objective: We aimed to explore the ability of textural heterogeneity indices determined by (18)F-FDG PET/CT for grading the malignancy of thymic epithelial tumors (TETs)., Methods: We retrospectively enrolled 47 patients with pathologically proven TETs who underwent pre-treatment (18)F-FDG PET/CT. TETs were classified by pathological results into three subgroups with increasing grades of malignancy: low-risk thymoma (LRT; WHO classification A, AB and B1), high-risk thymoma (B2 and B3), and thymic carcinoma (TC). Using (18)F-FDG PET/CT, we obtained conventional imaging indices including SUVmax and 20 intratumoral heterogeneity indices: i.e., four local-scale indices derived from the neighborhood gray-tone difference matrix (NGTDM), eight regional-scale indices from the gray-level run-length matrix (GLRLM), and eight regional-scale indices from the gray-level size zone matrix (GLSZM). Area under the receiver operating characteristic curve (AUC) was used to demonstrate the abilities of the imaging indices for differentiating subgroups. Multivariable logistic regression analysis was performed to show the independent significance of the textural indices. Combined criteria using optimal cutoff values of the SUVmax and a best-performing heterogeneity index were applied to investigate whether they improved differentiation between the subgroups., Results: Most of the GLRLM and GLSZM indices and the SUVmax showed good or fair discrimination (AUC >0.7) with best performance for some of the GLRLM indices and the SUVmax, whereas the NGTDM indices showed relatively inferior performance. The discriminative ability of some of the GLSZM indices was independent from that of SUVmax in multivariate analysis. Combined use of the SUVmax and a GLSZM index improved positive predictive values for LRT and TC., Conclusions: Texture analysis of (18)F-FDG PET/CT scans has the potential to differentiate between TET tumor grades; regional-scale indices from GLRLM and GLSZM perform better than local-scale indices from the NGTDM. The SUVmax and heterogeneity indices may have complementary value in differentiating TET subgroups.

Objectives: (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) plays an important role in many oncological settings. In this study, we assessed the utility of (18)F-FDG-PET for predicting the histological classification, stage and survival of thymic epithelial tumors., Methods: We retrospectively analyzed 37 patients with thymic epithelial tumors who underwent PET before surgical resection and investigated the relationship between the maximum of standardized uptake value (SUVmax) of each tumor and the WHO classification, recurrence-free survival, and tumor-related gene expressions., Results: The study included 15 males and 22 females, ranging in age from 22 to 81 years (mean 64 years). The tumor histology of 31 tumors was thymoma and that of the remaining tumors was thymic carcinoma. The Masaoka tumor stage was as follows: stage I in 18, II in 9, III in 5 and IV in 5 patients. The patients were divided into three groups according to a simplified histologic classification: low-risk thymoma (types A, AB and B1, n = 21), high-risk thymoma (types B2 and B3, n = 10) and thymic carcinoma (n = 6). The SUVmax of low-risk group (SUVmax ≤4.27) was significantly lower than that of high-risk group (p = 0.0114) and that of thymic carcinomas (SUVmax >4.27) was also significantly higher than that of thymomas (p < 0.0001). The group of high SUVmax (SUVmax >4.27) had significantly inferior recurrence-free survival to that of less value (SUVmax ≤4.27) (p = 0.0009). The SUVmax were not correlated with tumor-related gene expressions., Conclusion: The SUVmax of (18)F-FDG-PET reflects WHO classification of thymic epithelial tumors. High SUVmax predicts lower recurrence-free survival of the tumors.

Background: Positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose ((18)F-FDG) has been studied in thymic epithelial tumors. We evaluated the usefulness of (18)F-FDG PET for monitoring after treatment in unresectable thymic epithelial tumors., Method: Twelve patients with unresectable/metastatic thymic epithelial tumors underwent PET study with (18)F-FDG before and after chemotherapy or radiotherapy. Response and survival were analyzed according to the ratio of the peak standardized uptake value (SUV) of the tumor to the mean SUV of the mediastinum (T/M ratio)., Results: Partial response (PR) evaluated by Response Evaluation Criteria in Solid Tumors (RECIST) was noted in 4 (33%) of 12 patients, and partial metabolic response (PMR) was observed in 6 (50%) of 12 patients. PR was observed in 4 of 6 patients with PMR. In 6 patients with any response, the T/M ratio at post-treatment was significantly lower than at baseline (p = 0.0017). In 6 patients with stable disease (SD), stable metabolic disease (SMD) was observed in 5 by use of (18)F-FDG PET. No statistically significant difference of (18)F-FDG uptake between at baseline and post-therapy was observed in 6 patients with SD (p = 0.4157) and SMD (p = 0.8419). Although the overall survival after treatment showed no statistically significant difference between PMR and SMD or progressive metabolic disease in the whole group of patients including thymoma, a statistically significant difference in the overall survival was observed between 5 patients with PMR and 5 patients with non-PMR (p = 0.0280)., Conclusion: Our preliminary study suggests that (18)F-FDG PET is useful for monitoring response and outcome after treatment in unresectable thymic epithelial tumors.

A 55-year-old female had an abnormal shadow on chest radiograph. Computed tomography (CT) revealed a 26-mm tumor mass in the left upper lobe. No malignant findings were obtained by bronchoscopic cytology or histopathological diagnostics, but on positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) examination the maximum SUV was 9.01 in accordance with the tumor mass shadow on CT. Video-assisted thoracoscopic surgery was performed as clinically suspected of lung cancer, and the diagnosis was pulmonary mixed squamous cell and glandular papilloma (PMSGP). Primary PMSGP is extremely rare, and this is the first to describe the PET findings of this disease.