HPV Positive Squamous Cell Carcinoma of the Oropharynx. Are we Observing an Unusual Pattern of Metastases?

To describe the clinical, histopathologic, immunohistochemical and molecular features of human papilloma virus (HPV)+ squamous cell carcinomas of the oropharynx that had an atypical clinical course. Methods and Results: Four patients with HPV+ oropharyngeal squamous cell carcinoma (OPSCC) were identified retrospectively based on unanticipated clinical behavior. The histopathology, immunohistochemistry and molecular studies of both the primary tumor and the metastases were analyzed to look for any predictors to explain the clinical course. The four patients were all male (average age 55) who presented initially with a neck mass and had stage IVA disease. Three of the primary tumors were nonkeratinizing squamous cell carcinoma and one case was a hybrid tumor of both high-grade squamous cell carcinoma and nonkeratinizing type, and all were p16 and HPV 16/18 positive. All patients received concurrent chemoradiation as primary therapy and had a complete response. Disease-free survival ranged from 7 to 15 months and metastases in 3 patients occurred only in bone, including the sternum, humerus, clavicle, and vertebrae. In one patient, distant metastases were identified in the pancreas, liver, lung and skull base. All metastatic lesions were nonkeratinizing morphology and were p16 and/or HPV positive. Two patients died of their disease, one patient is alive with disease and one patient is disease-free. Although infrequent, unanticipated clinical outcomes can occur in HPV-related OPSCC including distant metastases and bone-only metastases. The tumor morphology of the metastases was comparable to the primary and retained p16 and HPV expression.