ERBB4 and head and neck squamous cell carcinoma: The ErbB family of receptor tyrosine kinases (RTKs)—Epidermal Growth Factor Receptor (EGFR), Human EGFR Related 2 (HER2), Human EGFR Related 3 (HER3) and Human EGFR Related 4 (HER4)—is implicated in HNSCC pathogenesis [42].