癌症多年來為十大死因之首，在惡性腫瘤的自然史中，口腔的轉移並不常見，其中最常轉移到下頜骨骨髓，而轉移到口腔中的軟組織或牙齦則極其少見。本院經歷一例肺癌的75歲男性，在做完放射治療1個月後因為下顎門齒動搖去拔除，傷口不易癒合，反而出現一快速長大的牙齦腫塊，此牙齦腫塊經組織學化驗為一具有巨大細胞的大型細胞癌，與其本身肺癌之細胞學特徵相同，此後病人僅接受支持性療法，於確認口腔轉移五個月後死於多重器官衰竭。此例提醒了當病患具呼吸、腸胃道腫瘤時，若有口腔不明腫塊，應注意是否有口腔轉移之可能性。

In the natural history of malignant tumours, oral metastasis is uncommon. Mandibular bone marrow is the most common site affected. Metastasis to the oral soft tissues or gingiva is extremely rare. A case of metastatic lung carcinoma to lower gingiva in a 75-year-old man is presented. The rapidly-growing gingival mass appeared at an unhealed tooth-extraction site one month after the completion of radiotherapy for lung carcinoma .The gingival tumor was histopathologically diagnosed as large cell carcinoma with giant cells which was identical to the cytological features of the previous lung carcinoma. The patient received supportive treatment but eventually died due to multi-organ failure. Therefore, more attention should be paid to the differential diagnosis of oral lesions if aerodigestive tract malignancy is present.