A rare presentation of an oral cavity metachronous malignancy: Case Report.

Introduction or background: Head and neck cancers, particularly those involving the oral cavity, are associated with high morbidity and mortality rates globally. Despite advancements in surgical techniques, chemotherapy, and radiotherapy, the development of second primary malignancies (SPMs) remains a critical concern for longterm survivors. The occurrence of metachronous double primary malignancies, where the second primary cancer arises at a different anatomical site and time, poses additional diagnostic and therapeutic challenges.

Case presentation: We present a rare case of a 42-year old male with a history of chronic tobacco use, diagnosed with metachronous double primary malignancies involving the left lateral border of the tongue and left buccal mucosa, separated by a disease-free interval of 15 months. The patient initially presented with a nonhealing ulcer and left cervical lymphadenopathy. Biopsy confirmed squamous cell carcinoma, and he underwent wide local excision with left radical neck dissection followed by adjuvant chemoradiation. Following a disease-free period of 15 months, the patient developed a second primary malignancy in the left buccal mucosa. After multidisciplinary discussions, the patient received palliative chemotherapy due to the extensive involvement of critical structures, including the infratemporal fossa.

Discussion and conclusion: The case highlights the clinical significance of field cancerization in head and neck cancer patients with long-term tobacco exposure, leading to the development of SPMs. It emphasizes the importance of ongoing surveillance, early detection strategies, and multidisciplinary approaches for optimal management. The case also underscores the complexities in distinguishing between recurrence and second primary malignancies, which have different treatment and prognostic implications. This report adds to the literature on SPMs and reinforces the need for vigilance in the follow-up of high-risk patients.