Discrepancy Between Clinical Diagnosis and Whole-exome Sequencing-based Clonality Analysis of Synchronous Multiple Oral Cancers

Abstract

Background/Aim: The definition of multiple oral cancers is based on the distances between the tumors. However, it is not possible to accurately predict tumor origins based only on clinical criteria. Patients and Methods: We performed whole-exome sequencing (WES) to analyze the genetic alterations in five tumors of two patients who underwent surgery in our hospital. Results: In case 1, the distances between tumors on the right mandibular gingiva and buccal mucosa were more than 15 mm, leading to a clinical diagnosis of multiple primary tumors. WES revealed common mutations between tumors, suggesting that the tumors were derived from the same clone. In contrast, in case 2, the distance between tumors on the right side of the tongue was only 10 mm, but the tumors were diagnosed as double primary tumors because their mutations were completely different. Conclusion: WES, rather than the available clinical criteria, can clarify the clonal origins of multiple oral cancers.