p16-Positive oropharyngeal squamous cell carcinoma metastasis to the thyroid following complete chemoradiotherapy response: a case report and review of the literature.

Metastasis of oropharyngeal squamous cell carcinoma (OPSCC) to the thyroid gland is rare, and p16-positive cases form an even smaller subset. We present a case of p16-positive thyroid metastasis from OPSCC identified after complete treatment response. Nine months after completing chemoradiotherapy, the patient developed throat pain and hoarseness. Computed tomography demonstrated an enlarged heterogeneous right thyroid gland and fine needle aspiration confirmed p16-positive metastatic OPSCC in the absence of locoregional recurrence. The patient underwent extended total thyroidectomy and right selective neck dissection; formal pathology confirmed metastatic OPSCC with involved margins and 13/22 positive lymph nodes. To our knowledge, this is the first reported intrathyroidal metastasis from p16-positive OPSCC after complete treatment response and in the absence of local recurrence. Further cases are required to better understand the epidemiology, optimal management, and prognosis of this presentation.