2. Suspected or histologically/cytologically confirmed OPSCC, stage II, III, or IVA (according to the AJCC 7th edition), or patients with loco-regional recurrence from an OPSCC primary, if time of recurrence is at least 6 months after completion of initial curative intent treatment (surgery or radiotherapy +/- chemotherapy or cetuximab). Patients with a suspected lesion may be enrolled and a baseline biopsy will be obtained as part of the study. If squamous cell histology is not confirmed, patients will be discontinued from the study