This sounds like the surgery was successful at dealing with the primary tumor. It is very common though for cells from that tumor to invade into the lymph drainage system, first in the cervical nodes of the neck. It doesn’t sound like in the process of your surgery they did any kind of neck dissection. That might mean that they are going to do that at a second surgery, or that they feel it is best addressed with radiation treatments or both. Please post back where they are with this so we might comment further. Dealing with any residual malignancy in the lymph system is important as that is a primary mechanism for it to spread to areas distant from the primary tumor.