DIANA JOHNSTON answered Anonymous' question 5/4/2012 What Is The Lump At The Base Of Dogs Tail? My dog is 19 yrs. Old and he has this big lump on the top of his tail near the base. It started out sorta small then it got another little bunp on top of the big one. It felt kind of squishy so I stuck it with a needle and now it has a … Read more