It is entirely possible the cancer point of origin is in the lymph node itself. More common is in a tonsil, which is also part of the lymph system particularly with HPV16 source.
As far as aggressive on a scale, that is subjective. Certainly aplastic cancers are extremely aggressive so that would be the 10 scale. Prostate cancer is usually very slow so we can rank the slow form as 1. SSC caught early I would put at the lower end say perhaps 3-4. All cancers if left untreated multiply exponentially for example 1,2,4,8,16,32 etc.
I know you are worried. You are in a battle not of your choosing and anyone would be scared and concerned. A million thoughts traverse the mind. However this cancer you have is very conquerable, better now than even twenty years ago when the odds were 85% successful when fully treated.
If you read several of the discussions in this group you will find many good pieces of advice such as the insistence of a feeding tube if the mouth or throat is involved. Proton radiation as opposed to photon for more accurate attack and less peripheral damage. Also make sure your oncologist and surgeon are well versed in head and neck cancers, not just cancers in general. Head and neck has some very specific issues to deal with. Because we don’t eat, breath, or think with our legs, you can radiate those parts until they fall off if necessary. The head is special so seek out the best.
Mayo’s main website mayoclinic.org in the search there is good information on Squamous Cell Carcinoma and you can look at MD Anderson in Houston,TX or the Cleveland Clinic to name others.