Genetic relationship between multiple squamous cell carcinomas arising in the oral cavity

Background: histological and clinical criteria are generally utilized to differentiate second primary tumors (SPT) from local recurrences (LR).. The purpose of the present study was to apply mtDNA D-loop analysis to differentiate SPT from LR and to validate the clinical classification. Methods: The study population consisted of 20 consecutive patients presenting multiple oral neoplastic lesions for a total of 25 paired lesions. mtDNA D-loop analysis was performed by direct sequencing and phylogenetic clusterization. Results: Agreement between mtDNA analysis and clinical classification was found in 19 cases. Discrepancies arose in 6 cases in which the clinical criteria based only on the spatial or temporal distance of the second lesion from the index tumor had led to a diagnosis of SPT (2 cases) or LR (4 cases). Conclusions: The present data highlight the value of mtDNA analysis in establishing the clonal relationship between the index tumor and the second neoplastic lesion.