Hi Magdelena

On a practical note,and maybe to answer your origonal question,cancer spreads via the lymphatic system.In your neck you have over a hundred lymph nodes that drain away fluid from your mouth .It just takes one cell from your tongue to get into the lymph glands,for the cancer to move to other parts of the body,and of course the neck and then the lungs are in the direct firing line.Hence so many people have large numbers of lymph nodes removed when they have their origonal surgery.
Did you have the primary site removed surgically?and did you have a neck dissection ? or did you just have radiotherapy and chemo?

This is a problematic development,but you have age on your side,so get all the information you can about your treatment plan,and then come back with any questions that you have.
there are plenty of folks here who will be able to help and advise.

liz