Trevor and I have picked up that the treatment he is going to be having is likely to have effects on his mouth and although we don't know where the primary is, his initial symptom was a lump in his neck. Following the excision he has had a tonsilectomy and a neck dissection so we relate to his cancer as head and neck, not mouth.
Mind you, we came across this great website as a result of searching in vain for information. Mouth cancer was the closest thing we could come up with and as it's turned out, we've been able to learn heaps from the info posted here. For our experience, head and neck cancers is how we relate to it.
Hope this gives you a view from another angle