Switching your cat back over to its species appropriate diet may have profound positive effects. If you’re up for a little bit of reading do a google search on Pottengers Cats.
When you say this is HUMONGUS…are you referring to the situation?? Or are you referring to a growth? If it’s a growth then maybe look into a drawing salve IF the growth isn’t near any organs. And again if it is a growth near the surface that is a fluid or fatty lipoma, instead of a “tumor”, then you may have success using frankincense essential oil topically to draw it out gently. BUT, I have limited knowledge and experience using drawing salves on tumors, so do some research….especially on the drawing salves as they can be used incorrectly.