EGFR and head and neck squamous cell carcinoma: Cellular EGFR expression, tumor cell density, plasma antibody concentration, and delivery barrier determined the fluorescent antibody distribution in tissue, which differentially translated to macroscopic tumor contrast depending on tumor size, tumor depth, and intraoperative imaging conditions in HGG, HNSCC, and LAC patients infused with an NIR-labeled EGFR antibody.