Metastasis of malignant tumors to the oral cavity: Systematic review of case reports and case series

Objective: To summarize published information regarding malignant tumors with metastasis to the oralcavity. Materials and methods: This was a systematic review with meta-analysis. An electronic search of Pubmed, Scopus, and Google Scholar databases from inceptions to February 2022 were performed. Only case reports or case series with histopathological results demonstrating metastasis to the oral cavity were included. The main outcomes included demographics, primary site, metastatic site, clinical manifestations, and patient survival. The quality of primary articles was assessed using the Joanna Briggs Institute - University of Adelaide scorecards for case reports and case series. Descriptive analysis and a Kaplan-Meier survival curve were performed. Results: 273 articles were selected (50 case series and 223 case reports), for a total of 950 cases. The mean age was 57.11 years. Males were more affected (57.5%). The most common primary sites in women and men was breast (29.8%), and lung (24.8%), respectively. In >> 1/3 of the cases, oral metastasis preceded tumor dissemination. Jawbones were more affected (56.7%) than soft tissues (37.9%), with the mandible being the most affected site (45.5%), followed by the gingiva (19.9%). The most common clinical manifestation was a mass or nodule. Most radiographic evidence was radiolucency of the jaw (60.6%). 3-year and 5-year survival rates were 14.2 and 10.7%. In the majority of cases, the primary tumor was the first to be diagnosed, while in 30.4%, metastasis was the first sign of the disseminated disease. This can be implied that the oral metastasis should be included in the differential diagnosis list of the oral diseases. Conclusion: Clinicians should be aware of the possibility of, albeit uncommon, oral metastases. Because the extracted data in this review was relatively generalized, the investigators cannot develop the diagnostic clues of oral metastasis, which require further investigations.