If breast cancer
occurs in a previously treated breast
, there's not much controversy about treating with mastectomy, as opposed to simple removal of the lump. In some cases, such as a very frail or elderly person, some would just do the local removal. More radiation can't be given, but chemo can and would be, depending on characteristics of the tumor. So, since the treatment would generally require mastectomy, it's reasonable to make the plans and proceed which saves a second anesthetic.