[Clinicopathological characteristics of HPV(+) oropharyngeal squamous cell carcinoma]

Objective: To observe the clinicopathologic features of oropharyngeal squamous cell carcinoma associated with human papilloma virus (OPSCC-HPV) and discuss the role and value of different in situ hybridization (ISH) detection methods for HPV in pathologic diagnosis. Methods: Fifteen cases of OPSCC-HPV were collected from Department of Pathology, Beijing Tongren Hospital, Capital Medical University from January 2016 to August 2018. These cases were diagnosed in accordance with the WHO classification of head and neck tumors. The histopathologic features and the clinicopathologic data were retrospectively analyzed. Immunohistochemistry (two-step EnVision method) was done to evaluate the expression of p16, Ki-67 and p53. ISH was used to detect HPV DNA (6/11 and 16/18). RNAscope technology was used to evaluate the presence of HPV mRNAs (16 and 18). Results: The mean age for the 15 patients (8 males, 7 females) was 47 years (range from 30 to 69 years). OPSCC-HPV typically presentedat an advanced clinical stage, six patients had cervical lymphadenopathy (large and cystic), seven had tonsillar swelling, one had tumor at base of tongue, and one had odynophagia. Microscopically the tumors exhibited distinctive non-keratinizing squamous cell carcinoma morphology. Cervical nodal metastases were large and cystic, with thickening of lymph node capsules. OPSCC-HPV raised from crypt epithelium and extended beneath the tonsillar surface epithelial lining as nests and lobules, often with central necrosis. Tumor cells displayed a high N: C ratio, and high mitotic and apoptotic rates. Tumor nests are often embedded within lymphoid stroma, and may be infiltrated by lymphoid cells.Fifteen cases (15/15) were strongly positive for p16; Ki-67 index were 60%-90%; they were focally positive or negative for p53. Ten cases (10/10) were negative for HPV 6/11 DNA, and one case(1/10) was focally positive for HPV16/18 DNA. Eleven cases (11/11) were strongly positive for HPV16 mRNA, one case was focally positive for HPV18 mRNA. Conclusions: OPSCC-HPV is a pathologically and clinically distinct form of head and neck squamous cell carcinoma. OPSCC-HPV is associated with high-risk HPV (type 16) in all cases. Detection of high-risk HPV16 mRNA by RNAscope is of great significance in the final diagnosis and pathogen identification.