What dose and treatment area of radiation should be given when p16+/HPV ISH negative SCC is found in the scar of a level V lymph node excisional biopsy with all other workup negative?  

It is difficult to give a detailed and nuanced response in one sentence. I would double-check that this is also EBER-negative, and if so, I would suspect a non-HN mucosal primary, possibly skin (as these can be p16+ve HPV -ve). As such, I would focus treatment on the involved neck. It sounds like, d...