一37歲女性因左側頸部腫塊就醫，經實時間超音波診斷為單一位於甲狀腺左葉中下方規則性低迴音實心結節，抽血診斷則呈亞臨床甲狀腺腺功能亢進。為進一步了解左側甲狀腺結節良惡性，病人接受甲狀腺細胞穿刺檢查，初步檢查懷疑濾泡性甲狀腺癌。為進一步鑑別診斷，因此安排一百微居里碘-131甲狀腺核子醫學掃描，結果顯示左側單一自主毒性功能結節，且抑制左側其他組織及右側甲狀腺功能。由於左側甲狀腺結節過大，病人接受手術切除治療，病理結果顯示為一良性甲狀腺腫瘤－結節性甲狀腺腫，而不是常見的致病因－甲狀腺瘤。對於甲狀腺細胞穿刺檢查中，約百分之十至二十屬未確定或懷疑性診斷，碘-131甲狀腺核子醫學掃描造影是一重要非侵性鑑別診斷工具，本文並將引用文獻討論自主毒性結節甲狀腺腫的分子生物機轉。

　　　　　We report a 34-year-old female with left neck mass. A well-defined mixed iso-hypoechoic solid thyroid nodule in the middle-low portion of left lobe of thyroid was diagnosed by real-time ultrasonography. Thyroid function test showed a pattern of subclinical hyperthyroidism. Follicular neoplasm was suspicious by fine needle aspiration cytology (FNAC). To further clarify the nature of the lesions, patient received the 131I scintigraphy which showed a solitary autonomously functioning thyroid nodule. The rest of the thyroid tissue was suppressed. The pathological finding revealed a rare pattern of benign nodular goiter. 131I thyroid scintigraphy remains as a useful procedure for differential diagnosis when fine needle aspiration cytology is indeterminate for malignancy. The possible mechanisms of nodular goiter with solitary autonomously functioning thyroid nodule seen on 131I thyroid scintigraphy will be discussed with literature reviews.