ERBB2 and head and neck squamous cell carcinoma: This study incorporates: (1) immunofluorescence and novel PET imaging to assess EGFR and HER2 expression in HNSCC, (2) in vitro live cell imaging of treatment synergy in three HNSCC cell lines, (3) PET imaging of hypoxia in response to combination HER2-targeted and EGFR-targeted therapies and (4) in vivo monitoring of longitudinal tumor changes in response to combination trastuzumab and cetuximab therapy.