Sasaki M, Kuwabara Y, Ichiya Y, Akashi Y, Yoshida T, Nakagawa M, Murayama S, Masuda K
Department of Radiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
J Nucl Med. 1999 Oct;40(10):1595-601.
We assessed the usefulness of PET studies in making a differential diagnosis of thymic tumors by using 11C-methionine (MET) and 18F-fluorodeoxyglucose (FDG).
We examined 31 patients with thymic tumors, including 14 patients with thymic cancer, 9 with invasive thymoma, 5 with noninvasive thymoma and 3 with thymic cysts. The histological diagnosis was confirmed by either surgery or biopsy. MET PET and FDG PET were performed in 28 and 29 patients, respectively. Both the MET and FDG uptakes were evaluated by the standardized uptake value (SUV).
MET uptake was not substantially different among thymic cancer (4.8 +/- 1.4), invasive thymoma (4.3 +/-1.1) and noninvasive thymoma (4.5 +/- 1.2), bat MET uptake in thymic cysts (0.9 +/- 0.1) was lower than that in the other three tumors (P < 0.01). The FDG uptake in thymic cancer (7.2 +/- 2.9) was higher than that in invasive thymoma (3.8 -/+ 1.3), noninvasive thymoma (3.0 +/- 1.0) and thymic cysts (0.9) (P < 0.01). MET uptake in thymic tumors correlated with the FDG uptake (r = 0.65), whereas MET uptake in thymic cancer was lower than FDG uptake (FDG/MET ratio = 1.52 +/- 0.52) but was higher than FDG uptake in both invasive and noninvasive thymoma (FDG/ MET ratio = 0.86 +/- 0.33). To differentiate thymic cancer from thymoma, a receiver operating characteristic (ROC) analysis was performed. The area under the curve of FDG PET was 0.90, whereas the FDG/MET ratio was 0.87.
The MET PET, FDG PET and the FDG/MET ratios were unable to differentiate benign thymic tumors from malignant ones, although FDG PET was considered to be useful in the differential diagnosis between thymic cancer and thymoma. Although the difference in the uptake ratio between FDG and MET suggests a different origin of the tumors, the FDG/MET ratio is not considered to be useful as a complementary method for the differential diagnosis of thymic tumors.
我们通过使用11C-蛋氨酸（MET）和18F-氟脱氧葡萄糖（FDG）评估了PET研究在胸腺肿瘤鉴别诊断中的作用。
我们检查了31例胸腺肿瘤患者，包括14例胸腺癌患者、9例侵袭性胸腺瘤患者、5例非侵袭性胸腺瘤患者和3例胸腺囊肿患者。组织学诊断通过手术或活检得以证实。分别对28例和29例患者进行了MET PET和FDG PET检查。MET和FDG摄取均通过标准化摄取值（SUV）进行评估。
胸腺癌（4.8±1.4）、侵袭性胸腺瘤（4.3±1.1）和非侵袭性胸腺瘤（4.5±1.2）之间的MET摄取无显著差异，但胸腺囊肿中的MET摄取（0.9±0.1）低于其他三种肿瘤（P<0.01）。胸腺癌中的FDG摄取（7.2±2.9）高于侵袭性胸腺瘤（3.8±1.3）、非侵袭性胸腺瘤（3.0±1.0）和胸腺囊肿（0.9）（P<0.01）。胸腺肿瘤中的MET摄取与FDG摄取相关（r = 0.65），而胸腺癌中的MET摄取低于FDG摄取（FDG/MET比值 = 1.52±0.52），但高于侵袭性和非侵袭性胸腺瘤中的FDG摄取（FDG/MET比值 = 0.86±0.33）。为了鉴别胸腺癌和胸腺瘤，进行了受试者操作特征（ROC）分析。FDG PET曲线下面积为0.90，而FDG/MET比值为0.87。
尽管FDG PET被认为在胸腺癌和胸腺瘤的鉴别诊断中有用，但MET PET、FDG PET及FDG/MET比值无法区分良性胸腺肿瘤和恶性胸腺肿瘤。虽然FDG和MET摄取率的差异提示肿瘤起源不同，但FDG/MET比值不被认为是胸腺肿瘤鉴别诊断的有用补充方法。
