Saw the vet. They can't tell whether it's benign or malignant without surgical removal of the lumps. The treatment process is pretty aggressive, and not guaranteed to work. The mortality rates in cats her age, with aggressive treatment, are approx 3 years. Without treatment, she could live for up to another two. The vet said that needle biopsies (least invasive detection) almost always give inconclusive results due to filling with blood, that if we were going to give her a general anaesthetic for xrays (which MAY show a spread to the chest) we should get the op done - the op being a strip mastectomy, very painful and massively intrusive. It's also astronomically expensive. So, we have decided to let our little old blue lady live out her remaining time, whatever that may be, in peace and without inflicted pain. If it's benign, she could live another however many years. If it's malignant, which we think it probably is, up to two. She's 14. We're gonna look after her carefully, with all the cuddles she needs and a treat of tuna once a week, until it's time for the long sleep. That will be decided if/when her behaviour changes to indicate pain, or if the lumps ulcerate. A horrible upsetting decision to make, but we think it's the right one for her, so we must face it head on and not spend the rest of her time fretting. I didn't even know cats could get breast cancer.