There are lots of articles written about treatment of the neck where there is no palpable lymphadenopathy. Some adopt a wait and see approach, while others will follow a more aggressive course under the theory that microscopic cancer could exist in the lymph nodes that would not necessarily show up to palpation, CT or PET.

There is very little "mandatory" here. At our support group yesterday, there were several who had a full course of radiation to the neck, even without palpable node involvement. Probably an equal number did not.