A B S T R A C T PurposeTo investigate the prognostic value of the BRAF V600E mutation and the recently identified TERT promoter mutation chr5:1,295,228CϾT (C228T), individually and in their coexistence, in papillary thyroid cancer (PTC). Patients and MethodsWe performed a retrospective study of the relationship of BRAF and TERT C228T mutations with clinicopathologic outcomes of PTC in 507 patients (365 women and 142 men) age 45.9 Ϯ 14.0 years (mean Ϯ SD) with a median follow-up of 24 months (interquartile range, 8 to 78 months). ResultsCoexisting BRAF V600E and TERT C228T mutations were more commonly associated with high-risk clinicopathologic characteristics of PTC than they were individually. Tumor recurrence rates were 25.8% (50 of (HR, 8.51; 95% CI, 4.84 to 14.97), which remained significant after clinicopathologic cofactor adjustments. Diseasefree patient survival curves displayed a moderate decline with BRAF V600E or TERT C228T alone but a sharp decline with two coexisting mutations. ConclusionCoexisting BRAF V600E and TERT C228T mutations form a novel genetic background that defines PTC with the worst clinicopathologic outcomes, providing unique prognostic and therapeutic implications.

Human papillomavirus-associated head and neck squamous cell carcinomas (HPV-HNSCC) originate in the tonsils, the major lymphoid organ that orchestrates immunity to oral infections. Despite its location, the virus escapes immune elimination during malignant transformation and progression. Here, we provide evidence for the role of the PD-1:PD-L1 pathway in HPV-HNSCC immune resistance. We demonstrate membranous expression of PD-L1 in the tonsillar crypts, the site of initial HPV infection. In HPV-HNSCCs that are highly infiltrated with lymphocytes, PD-L1 expression on both tumor cells and CD68+ tumor associated macrophages (TAMs) is geographically localized to sites of lymphocyte fronts, while the majority of CD8+ tumor infiltrating lymphocytes (TILs) express high levels of PD-1, the inhibitory PD-L1 receptor. Significant levels of mRNA for interferon-γ (IFN-γ), a major cytokine inducer of PD-L1 expression, were found in HPV+ PD-L1(+) tumors. Our findings support the role of the PD-1:PD-L1 interaction in creating an “immune-privileged” site for initial viral infection and subsequent adaptive immune resistance once tumors are established and suggest a rationale for therapeutic blockade of this pathway in patients with HPV-HNSCC.