When my husband began feeling the 'soreness' in his neck (after having a mole removed from his back), the suggested a FNA (fine needle aspiration) to biopsy his lymph fluid. Have you asked if they can do an FNA on the lymph nodes in question? He had an FNA done by just 'feeling' the node as it was visible - or at least you could feel it's size if you were to press on his neck. He had another one done with the help of an ultrasound, to help guide the needle.
I don't know the details of your situation or if this is even an option, but I would definitely ask.
Blessings,
Rhonda Sparks
www.uvskinz.com