PIK3CA and head and neck squamous cell carcinoma: Even though the RTK-RAS-PI3K (62% in HPV-negative versus 61% in HPV-positive), cell death (44% in HPV-negative versus 31% in HPV-positive), immunity (7% in HPV-negative versus11% in HPV-positive), differentiation (64% in HPV-negative versus 44% in HPV-positive) and oxidative stress (22% in HPV-negative versus 3% in HPV-positive) pathways have been found to be deregulated in both groups with different frequencies (Figure 2), and, the prognosis has been found to be better in HPV-positive HNSCC cases [34].