IGF1R and head and neck squamous cell carcinoma: Similar to other cancer entities, receptor tyrosine kinases (RTKs) such as the insulin-like growth factor 1 receptor (IGF1R) [3], the MET proto-oncogene receptor tyrosine kinase (MET) [4], the vascular endothelial growth factor receptor (VEGFR) [5], the fibroblast growth factor receptor 1 (FGFR1) [6], and, especially, the epidermal growth factor receptor (EGFR) [7,8] have been explored as potential targets in HNSCC.