ERBB2 and breast cancer: Erb‐b2 receptor tyrosine kinase 2 (ERBB2; also known as HER2) expression is observed in 25–40% of head and neck squamous cell carcinomas (HNSCC), yet there are no anti‐HER2 therapies under evaluation for HNSCC, as conventional cytostatic anti‐HER2 antibodies have had limited effectiveness and levels of HER2 overexpression are lower in HNSCC tumors compared to breast cancer.