As part of the removal of the forepart of my tongue and replacement with a 'free flap' (new tongue front built from various tissues harvested from my wrist), the surgeon removed the lymph glands under my chin -- He connected the blood vessels from my free flap to the vessels in where the glands were.

He made the comment to me that after the need for the lymph system in youth, he considers them to now just be "repositories for cancer cells".

I would guess that it is up to the practice of the surgeon and the location of the glands with respect to the primary cancer site as to how much additional removal work would be done.

BTW, the PET/CT/MRI scans prior to my surgery indicated that the cancer was limited to my tongue and the biopsies, including the lymph tissue) bore that out.