A Rare Oral Metastatic Lesion as the Initial Diagnosis of Small Cell Lung Cancer: Case Report and Systematic Review

Objectives: This study aims to describe a rare case of oral metastasis from small-cell neuroendocrine carcinoma originating from the lung and to perform a systematic review of the cases reported in the literature. Methods: We present the case of a patient with oral metastasis from small-cell neuroendocrine carcinoma of the lung. The patient presented at the clinical examination with severe pain in the attached gingiva in the 3.5 region, extracted one month earlier, despite prolonged antibiotic therapy. A systematic review of the literature was conducted using the PubMed, Scopus and Web of Science databases, in accordance with the PRISMA 2020 guidelines for systematic reviews. Results: A biopsy of the affected area was performed. The histological and immunohistochemical analysis revealed a fragment with features compatible with a secondary lesion with probable origin from the lung. In addition, a review of the existing English-language literature was carried out and revealed a total of six cases of oral metastasis. Conclusions: Oral metastases from small-cell neuroendocrine carcinoma are rare but have been reported in the literature. The gold standard for diagnosis remains histological examination.