Hello, more than likely this is also a mammary tumor that has developed in your baby. For some reason some dogs get different types of tumors and masses in tha mammory area. I would have the tumor removed at this point and then biopsied to try and figure out just what type of tumor it is. That way the appropriate medication and treatment can begin. I am going to send you a link to some information on mammory tumors. If you need anything else please be sure to let me know.