GPs bleeding from nipples

Question
There is a lump under the skin around the nipple area, which has appeared in the last month. There is now blood seeping from the nipple. My GP is about four years old and other than this (and being a little over wieght) she seems fine.
I shall take her to the vet but any ideas.  

Answer
It is most likely a mammary gland tumor, most are benign, not cancerous, in guinea pigs, but since it is bleeding instead of ozzing an opaque liquid it is most likely a tumor. It can be removed by a vet, most of the time they will just remove the whole nipple that is affected. It could also possibly be a cyst, being in that area though tumors are more common. Since the pig is older the vet may just want to leave it alone and just give the pig pain medication depending on the size of it, often when you start messing with tumors things can just get worse. If it is just a cyst or infection, the vet will just need to drain the area and give you pig antibiotics, but she does need to see a vet, it is not really something you can deal with at home. Until then try to use a soft type of bedding in the cage and keep the area around the nipple clean so it doesn't get a secondary infection. Let me know if you have any questions.
Brittany