Liu R S, Yeh S H, Huang M H, Wang L S, Chu L S, Chang C P, Chu Y K, Wu L C
National PET/Cyclotron Center and Department of Nuclear Medicine, Taipei Veterans General Hospital, and National Yang-Ming University School of Medicine, Taipei, Taiwan.
Eur J Nucl Med. 1995 Dec;22(12):1402-7. doi: 10.1007/BF01791148.
Thymomas are lacking in malignant cytological features. Their staging is defined by the invasiveness of the tumour. This study aimed to analyse the uptake patterns of fluorine-18 fluorodeoxyglucose (FDG) in thymomas of different stages. FDG positron emission tomography (PET) scan was performed in 12 patients suspected of having thymoma and in nine controls. Qualitative visual interpretation was used to detect the foci with FDG uptake higher than that of normal mediastinum. Tumour/lung ratio (TLR) was calculated from the counts of ROIs over the mass and over comparable normal lung tissue in thymoma patients. Mediastinum/lung ratio (MLR) was calculated from the counts of ROIs over the anterior mediastinum and lung in controls. The PET scan patterns of distribution of foci with FDG uptake and TLRs were correlated with the computed tomography (CT) or magnetic resonance imaging (MRI) findings, and staging of the thymomas. Thymectomy was performed in ten patients and thoracoscopy was done in two patients. The results revealed ten thymomas (two stage I tumours, two stage II, four stage III and two stage IV, according to the Masaoka classification), and two cases of thymic hyperplasia associated with myasthenia gravis. Myasthenia gravis was also noted in four thymoma patients. FDG studies showed (a) diffuse uptake in the widened anterior mediastinum in patients with thymic hyperplasia, (b) confined focal FDG uptake in the non-invasive or less invasive, stage I and II thymomas, and (c) multiple discrete foci of FDG uptake in the mediastinum and thoracic structures in stage III and IV advanced invasive thymomas. The thymomas had the highest TLRs, followed by the TLRs of thymic hyperplasia and the MLRs of control subjects (P <0.005). No significant difference was found between thymomas in different stages or between thymomas with and thymomas without myasthenia gravis. In comparison with CT and/or MRI, FDG-PET detected more lesions in patients with invasive thymomas and downgraded the staging of thymoma in four patients. Our preliminary results suggest that FDG-PET is useful in the assessment of the invasiveness of thymomas, and may have the potential to differentiate thymomas from thymic hyperplasia.
胸腺瘤缺乏恶性细胞学特征。其分期由肿瘤的侵袭性决定。本研究旨在分析不同分期胸腺瘤中氟-18氟脱氧葡萄糖（FDG）的摄取模式。对12例疑似胸腺瘤患者和9例对照者进行了FDG正电子发射断层扫描（PET）。采用定性视觉解读来检测FDG摄取高于正常纵隔的病灶。通过胸腺瘤患者肿块及可比正常肺组织上感兴趣区（ROI）的计数计算肿瘤/肺比值（TLR）。通过对照者前纵隔和肺上ROI的计数计算纵隔/肺比值（MLR）。FDG摄取病灶的PET扫描分布模式及TLR与计算机断层扫描（CT）或磁共振成像（MRI）结果以及胸腺瘤的分期相关。10例患者接受了胸腺切除术，2例患者接受了胸腔镜检查。结果显示有10例胸腺瘤（根据Masaoka分类，2例为I期肿瘤，2例为II期，4例为III期，2例为IV期），以及2例与重症肌无力相关的胸腺增生病例。4例胸腺瘤患者也存在重症肌无力。FDG研究显示：（a）胸腺增生患者增宽的前纵隔内弥漫性摄取；（b）I期和II期非侵袭性或侵袭性较小的胸腺瘤内局限性FDG摄取；（c）III期和IV期侵袭性进展期胸腺瘤的纵隔和胸部结构内多个离散的FDG摄取病灶。胸腺瘤的TLR最高，其次是胸腺增生的TLR，对照者的MLR最低（P<0.005）。不同分期胸腺瘤之间或伴有与不伴有重症肌无力的胸腺瘤之间未发现显著差异。与CT和/或MRI相比，FDG-PET在侵袭性胸腺瘤患者中检测到更多病灶，且使4例患者的胸腺瘤分期降低。我们的初步结果表明，FDG-PET有助于评估胸腺瘤的侵袭性，且可能有潜力区分胸腺瘤与胸腺增生。
