本文主要報告一位有鎖骨病理性骨折的46歲男性病人，被安排一系列之檢查，包括電腦斷層掃描、腹部超音波等等，但臨床上卻找不到確定的原發性腫瘤，故進一步安排氟-18-去氧葡萄糖（FDG）的全身正子造影（PET）檢查來尋找原發性腫瘤以及評估全身轉移的情形。此病例再一次印證了PET在尋找原發性腫瘤及評估全身轉移上的高度價值。

　　　　　At present, metastatic bone disease is usually assessedusing technetium-99m-methylene diphosphonate (99mTc-MDP) whole body scan, which is a sensitive but nonspecific method for evaluation of osseous metabolism. Several studies have shown that fluorine-18-fluorodeoxyglucose positron emission tomography (18F-FDG PET) is a useful imaging tool for detection of bone metastases and differentiation of benign and malignant lesions. Another advantage of 18F-FDG PET is that all organ systems can be visualized and evaluated in a single whole-body imaging session. We present a case of a 46-year-old male patient with suspected bone metastases from unknown primary cancer who was placed in an oncology screening program that included 18F-FDG PET whole-body scan for primary tumor detection and staging.