Abstract
BACKGROUND: Oral metastatic tumor from a rectal adenocarcinoma is very uncommon. The primary site is usually assumed based on the past clinical history. In the case of oral metastatic tumors, they commonly have a poor prognosis because often they have already spread to other sites. CASE PRESENTATION: We present the case of a 64-year-old male patient with secondary metastasis to the mandibular gingiva via lung metastasis after the surgical resection of a primary rectal adenocarcinoma. The gingival lesion grossly appeared as a swollen mass, making mastication difficult. The patient received palliative radiotherapy for the mandibular mass lesion. However, tumor reduction was accompanied by the development of pneumonia and deterioration of the patient's cachexia. Thus, the radiotherapy was discontinued but the patient died 2 months postradiotherapy. In the long term after its primary resection, the rectal adenocarcinoma was deduced to have finally metastasized to the oral region. CONCLUSIONS: In this case, we consider a distant secondary metastasis to the oral region from a rectal malignancy. In such cases, careful clinical and pathologic evaluations are necessary, with careful consideration of the inclusion of palliative treatment in the therapeutic management.