從非口腔部位的惡性腫瘤轉移至齒齦是非常罕見。約佔所有轉移口腔病例比率百分之四以下。遠端癌症轉移到口腔軟組織，以肺癌和乳癌最常見。除頸部與鎖骨上淋巴結之外，直腸癌轉移至口腔極為少見。本文報告一位由直腸腺癌轉移至齒齦的罕見病例。雖然齒齦轉移的預後相當差，但是給予局部放射治療是對於這嚴重疾病的遠端轉移之一種有效的姑息性療法。

Metastatic tumors to gingival from non-oral malignancies are very uncommon. It accounts only for less than 4% of all metastatic tumors to the oral cavity. The lung and breast are the most common distant primary sites for metastasis to oral soft tissue. Metastases from the rectal cancer to oral cavity and neck region are extremely rare, except to neck and supraclavicular lymph node. We will describe a rare case of primary adenocarcinoma of rectum with metastasis to the gingiva of the mouth. Although the prognosis of patients with gingival metastasis is felt to be poor, regional radiotherapy is effective for the palliative purpose to the local metastatic lesion of the advanced disease.