Relevance of tumour-infiltrating lymphocytes in oral mucosal melanoma: a systematic review

Oral mucosal melanoma (OMM) is a rare and aggressive malignancy with a generally poor prognosis. Reliable prognostic markers for OMM are scarce, complicating disease management and patient counselling. Tumour-infiltrating lymphocytes (TILs) have shown prognostic value in other cancers, but their potential as a biomarker in OMM is not yet well defined. Hence, a systematic literature review, following the PRISMA guidelines, was conducted. The PubMed and Embase databases were searched for studies reporting on TILs in five or more OMM patients. Two studies reporting 102 OMM patients met the inclusion criteria and were included. Despite differences in TIL assessment methods and cut-offs, approximately 25% of OMM patients had demonstrable TILs. High TIL levels were associated with improved overall survival, although this reached statistical significance in only one study, describing 20 patients. In one study, low TIL levels were significantly associated with an increased risk of distant metastasis. Overall, despite the limited number of included studies, the findings suggest that TILs may serve as a prognostic marker in OMM, with higher TIL levels indicating more favourable outcomes. Larger, standardized studies are needed to validate these preliminary observations, refine TIL assessment methodologies and cut-off values, and to explore interactions with other prognostic markers. Ultimately, integrating the evaluation of TILs into OMM prognostic models could enhance patient stratification, guide treatment planning, and improve patient counselling.