背景與目的：18-氟-2-去氧葡萄糖（FDG）正子斷層造影（PET）對原發性腎細胞癌（RCC）的檢測靈敏度較低。然而，有證據顯示FDG PET或PET/電腦斷層掃描(CT)是檢測RCC患者轉移性或復發性病變的重要工具。本研究旨在探討腎細胞癌的生長是否可能轉變為FDG代謝與轉移。研究方法：我們回顧了在我們機構的正子斷層造影(PET)中心看到的22例RCC（透明細胞型）患者的病歷。在這 22 名患者中，14名患者在FDG PET/CT掃描中偶然發現腎臟病變，並經組織病理學證實RCC無轉移（作為 A 組）。8例RCC患者全身FDG PET/CT掃描均有腎外轉移病灶（B組）。研究結果：我們研究中所有患者的基線特徵之間的關係，發現腫瘤大小與腎腫瘤中FDG 攝取的SUVmean(r=0.80，p<0.001)呈正相關。此外，轉移狀態與 SUVmean(r=0.64,p=0.001)以及腫瘤大小(r=0.66,p=0.001)之間存在正相關。當RCC腫瘤大小大於4cm且視覺評分大於1被用作我們研究中的截止值時，曲線下面積(AUC)為0.902（95% CI：0.77-1.00），靈敏度和特異性為100%和85.7%。結論：FDG PET/CT顯示大於4cm的RCC生長可能轉變為FDG代謝和轉移。

Background and purpose: F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has a low sensitivity for primary renal cell carcinoma (RCC) de-tection. Then, evidence suggests that FDG PET or PET/computed tomography (CT) is a valuable tool in the detection of metastatic or recurrent lesions in patients with RCC. This study aims to explore whether renal cell carcinoma growth may change into FDG metabolism associated with metastasis. Methods: We reviewed retrospectively the medical records of 22 patients with RCC (clear cell type) seen at our institution’s PET center. Of these 22 patients, 14 patients have an incidental finding of renal lesion on FDG PET/CT scans and histopathologically proven RCC without metastasis later (as group A). 8 patients have RCC with extra-renal metastasis lesion on FDG PET/CT scans of the whole body (as group B). Results: Talking about the relationship among baseline characteristics of all patients in our study, a positive correlation was found in tumor size between with SUVmean (r=0.80, p<0.001) of FDG uptake in the renal tu-mor. In addition, there was a positive correlation between metastasis status and SU-Vmean (r=0.64, p=0.001) as well as tumor size (r=0.66, p=0.001). When an RCC tu-mor size larger than 4 cm and a visual score larger than 1 were used as the cutoff value in our study, the area under the curve (AUC) was 0.902 (95% CI: 0.77-1.00), with sensitivity of 100% and specificity of 85.7%. Conclusion: FDG PET/CT shows RCC growth larger than 4 cm may change into FDG metabolism and metastasis.