Molecular events in relapsed oral squamous cell carcinoma: Recurrence vs secondary primary tumor

•Relapses have a great impact on both the morbidity and mortality rates of oral squamous cell carcinoma (OSCC) patients.•Molecular techniques add to the further understanding of these lesions and may provide tools for clinical management.•This review discusses the limitations of the current OSCC relapse classification method.•The manuscript presents possible alternatives to improve this classification based on molecular techniques.

SummaryRelapses have a great impact on both the morbidity and mortality rates of oral squamous cell carcinoma (OSCC) patients. Current classification criteria are imprecise and need improvements. Recent advances in understanding of OSCC relapses on a molecular level provide new possibilities to better classify true recurrences and second primary tumors. This review discusses the limitations of the current OSCC relapse classification method and presents possible alternatives to improve this classification based on molecular techniques. Moreover, these molecular techniques add to the further understanding of these lesions and may provide tools for clinical management.