Clinicopathologic Analysis of HPV-Related Primary Squamous Cell Carcinoma of the Thyroid

Object: This study aims to explore the clinical and pathologic characteristics of HPV-related primary thyroid squamous cell carcinoma (PSCCT), a rare tumor classified by WHO-5 as a subtype of anaplastic thyroid carcinoma (ATC). Methods: Clinical data, histomorphology, immunohistochemistry, HPV detection, and B-raf gene point mutations of 3 PSCCT cases were analyzed. Subsequent follow-up was conducted post-treatment. Results: All 3 cases involved female patients aged between 60 and 76. Microscopic examination revealed squamous cell carcinoma in cases 1 and 3, whereas case 2 exhibited both squamous cell carcinoma and papillary thyroid carcinoma components. Immunohistochemistry demonstrated CK19, PAX8, and TTF1 expression in the papillary thyroid carcinoma component, and CK5/6, p63, p40, and PAX8 expression in the squamous cell carcinoma component. P16 exhibited diffuse positivity in both squamous cell carcinoma and classic papillary carcinoma. HPV analysis identified low-risk type 6 positivity in cases 1 and 3, while both squamous cell carcinoma and papillary carcinoma areas in case 2 were positive for HPV-33. B-raf gene mutation was exclusive to case 2. Conclusion: Diagnosis of PSCCT necessitates multidisciplinary assessment, incorporating clinical symptoms, imaging, histomorphology, and immunohistochemistry. This study, for the first time, reveals the presence of HPV DNA in both PTC and PSCCT, occurring concurrently but separately. Given the limited scope of 3 case reports, definitive conclusions cannot be drawn, warranting further investigation.