Atypical Metastasis of p16-Positive Tonsillar Squamous Cell Carcinoma to the Pleura: A Case Report.

Incidence rates and patterns of distant metastases of head and neck malignancies are well documented in the literature, such that focused management strategies are routinely practiced in anticipation of their likely behavior. Head and neck tumors are known to most commonly metastasize to the lungs, skeletal system, and liver, generally within 2 years of definitive treatment and in the context of poor locoregional control of the primary lesion. Recent studies, however, have shown that human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (SCCa) tumors display different patterns of distant metastases than those traditionally described for head and neck HPV-negative SCCa tumors. This finding has substantial implications for how patients undergoing treatment of these cancers should be surveilled after therapy. This report describes a case of p16-positive tonsillar SCCa with metastasis to a highly unusual secondary site in the pleura to show an example of the unconventional patterns of distant metastases reported for HPV-positive oropharyngeal SCCa in the recent literature. We aim to provide a more thorough understanding of this case by discussing the pathogenesis of metastatic spread to the pleura and the clinical progression generally observed in patients with secondary pleural malignancy. This report goes on to investigate how behaviors of distant metastases exhibited by HPV-positive oropharyngeal SCCa differ from those of more conventionally described head and neck HPV-negative SCCa and the implications thereof for strategies of post-treatment surveillance of these tumors going forward.