A Case Report on the Treatment of Synchronous Multiple Primary Cancers Originating in the Base of the Tongue and Supraglottis

Synchronous multiple primary cancers occurring in the head and neck region are a relatively rare clinical scenario; distinguishing whether anatomically adjacent lesions represent a single continuous lesion or independent primary lesions has a direct impact on the determination of treatment strategies. The authors report a case of synchronous multiple primary cancer involving the base of the tongue and the supraglottic region. In a 59-year-old man, flexible laryngoscopy revealed non-contiguous papillary masses in the left base of the tongue and the left supraglottic region. Findings from neck computed tomography (CT), magnetic resonance imaging (MRI), PET-CT, and suspension laryngoscopy showed no anatomical continuity between the two lesions, and there were no signs of cervical or distant metastasis. Pathologically, the supraglottic lesion was diagnosed as squamous cell carcinoma, while the base of the tongue lesion showed findings consistent with high-grade dysplasia or higher. Considering the imaging findings suggestive of malignancy and the results of immunohistochemical staining, it was judged reasonable to interpret the latter as a malignant lesion. Accordingly, the two lesions were interpreted as synchronous multiple primary cancer rather than a single continuous lesion. Through a multidisciplinary approach, the anatomical location of the lesions, the anticipated extent of resection, and the importance of functional preservation were comprehensively considered, and concurrent chemoradiotherapy was administered. This case demonstrates that distinguishing between a continuous lesion and synchronous multiple primary cancer in adjacent head and neck lesions can alter the actual treatment strategy, and suggests the importance of a multidisciplinary approach that considers not only oncological outcomes but also anatomical location and functional preservation when making treatment decisions.