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Abstract
Primary mediastinal germ cell tumor (MGCT) is an uncommon tumor. Although it has histology similar to that of gonadal germ cell tumor (GCT), the prognosis for MGCT is generally worse than that for gonadal GCT. We performed visual assessment and quantitative analysis of [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) for MGCTs. A total of 35 MGCT patients (age = 33.1 ± 16.8 years, F:M = 16:19) who underwent preoperative PET/CT were retrospectively reviewed. The pathologic diagnosis of MGCTs identified 24 mature teratomas, 4 seminomas, 5 yolk sac tumors, and 2 mixed germ cell tumors. Visual assessment was performed by categorizing the uptake intensity, distribution, and contour of primary MGCTs. Quantitative parameters including the maximum standardized uptake value (SUVmax), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and maximum diameter were compared between benign and malignant MGCTs. On visual assessment, the uptake intensity was the only significant parameter for differentiating between benign and malignant MGCTs (p = 0.040). In quantitative analysis, the SUVmax (p < 0.001), TBR (p < 0.001), MTV (p = 0.033), and TLG (p < 0.001) showed significantly higher values for malignant MGCTs compared with benign MGCTs. In receiver operating characteristic (ROC) curve analysis of these quantitative parameters, the SUVmax had the highest area under the curve (AUC) (AUC = 0.947, p < 0.001). Furthermore, the SUVmax could differentiate between seminomas and nonseminomatous germ cell tumors (p = 0.042) and reflect serum alpha fetoprotein (AFP) levels (p = 0.012). The visual uptake intensity and SUVmax on [18F]FDG PET/CT showed discriminative ability for benign and malignant MGCTs. Moreover, the SUVmax may associate with AFP levels.

Affiliations

Koeun Lee 1 2, Yong-Il Kim 3, Jungsu S Oh 2, Seung Yeon Seo 2, Jae Kwang Yun 4, Geun Dong Lee 4, Sehoon Choi 4, Hyeong Ryul Kim 4, Yong-Hee Kim 4, Dong Kwan Kim 4, Seung-Il Park 4, Jin-Sook Ryu 2
1Department of Nuclear Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
2Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
3Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea. kyi821209@naver.com.
4Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.