Are Histomorphological Features Predictive of p16 Immunopositivity Different for Oral and Oropharyngeal Squamous Cell Carcinoma?

Relevance of Partial p16 Immunostaining in Oral Squamous Cell Carcinoma and Co- Relation with HPV DNA Status

INTRODUCTION

Immunostaining criteria for p16 positivity in oropharyngeal squamous cell carcinoma have been laid down by College of American Pathologists (CAP) and the American Society of Clinical Oncology (ASCO). The staining should be of moderate to strong intensity seen in 70 percent of the tumor cells. Recent studies have pointed out that a small minority of cases are missed using p16 as the surrogate marker at above mentioned cut off. By convention the same criteria have been used for oral squamous cell carcinoma.

MATERIAL AND METHODS

The authors revisited the results of their previous study where immunohistochemistry for p16 was found to be positive by AJCC criteria in 139 out of 800 cases of oral squamous cell carcinoma. For this study, all the p16 immunonegative cases (by AJCC criteria) were analysed again for partial staining patterns, defined for this study as cases with 50-75% cells showing 2+/3+ intensity of nuclear p16 immunostaining and for basal predominant pattern of immunostaining. These cases were subjected to HPV DNA PCR.

RESULTS

Out of the 661/800 cases found to be negative for p16 immunohistochemistry, a total of 34/800(4.25%) showed partial staining based on the criterion of 50-75% cells showing p16 immunostaining intensity of 2/3+.The basal predominant pattern of immunostaining for p16 was seen in 43/800 (5.38%) cases. When these cases were subjected to HPV DNA analysis, 11/34 (32.35%) of the cases showing partial staining and 02/43 (4.7%) of the cases showing basal predominant pattern of p16 immunostaining were found to be HPV-DNA positive.

CONCLUSION

The inclusion of partial immunostaining patterns of p16 in HPV analysis of oral squamous cell carcinoma can improve our understanding of HPV driven oral squamous cell carcinoma.

Negative Prognostic Implication of TERT Promoter Mutations in Human Papillomavirus-Negative Tonsillar Squamous Cell Carcinoma Under the New 8th AJCC Staging System

Telomerase reverse transcriptase gene promoter (TERTp) mutation is a potential candidate for pathogenesis and therapeutic target of tonsillar squamous cell carcinomas (TSCCs) in association with human papillomavirus (HPV). Their clinical relevance has not been validated under the new 8th American Joint Committee on Cancer (AJCC) staging system. We analyzed real-time peptide nucleic acid–mediated PCR and sequencing methods (TERTp mutation) and real-time PCR-based assay (HPV) in 80 surgically resected TSCCs. The 8th edition staging system improved the stratification of the early and advanced stages and between T or N categories for overall survival over the 7th edition. TERTp mutation was found in 7.5%, and HPV in 80.0% of the patients. The majority (83.3%) of TERTp mutation cases were HPV-positive TSCCs. Applying the 8th edition staging system, TERTp mutation was an independent factor of poor prognosis for disease-free survival (DFS) in TSCC patients, supporting the clinical significance of TERTp mutation in tonsil cancer. TERTp mutations were also negatively correlated with overall survival and DFS in HPV-negative TSCCs. Conclusively, TERTp mutation provides negative prognostic impact on survival of surgically managed tonsil cancers staged with the AJCC 8th edition.