Rumors of his death...

 ...were greatly exaggerated? It's only been about a couple weeks since his diagnosis, but Mittens is either doing a very cat-like thing and fooling his humans, or he is legitimately feeling better even though we have radiographic evidence of a dime-sized tumor in his abdomen. He spends most of each day on the living room couch doing typical cat stuff. He's eating lots of baby food and other soft foods and does not care at all about the dog anymore. They are often face-to-face and Yeager has simply backed down, there's no other word for it.