aging female dogs

Question
my question is about my 13 year old female dog.her name is tasha.is there a condition in older females(she has never had puppies and has not been fixed)that would cause her breast to swell? a couple of years ago she had one of her nipples that starting sagging. it now looks like one of those "water ballons"that we had when i was a kid.i have been out of work now for 3 years with a disability and even though it's killing me, a trip to the vet just hasn't been an option.although i have been giving her all of her shots myself.none of her day to day activities have changed in reguards to eating,water intake bowel movements or her wanting to walk and play.when people see her the first question is "did she just have puppies".what ever it is it seems to worry me much more than it does her.but because it,s one of the back breast i've noticed lately.she has started hesitating a bit when it comes to running,or jumping up on the bed or into the car.it's quite heavy and hangs down almost in bettween her back legs.tashas weights about 55 or 60 pounds.and doesn't seem to have any problems with arthritis(wish i could say the same for myself).i had a male dog that passed away before i got tasha.he developed something that looked like what hers does,except his was locatated just to the one side at the base of his tail. it also got about the size of a softball.his vet at the time ruled out cancer.he said it would start to drain on it's own which it did.it happened when he was about the same age as tasha is now,and he lived to be 18 years old he to was about the same weight or larger than my tasha.if it helps any tasha's daddy was a rotwilier and her mom was a shepeard mix.god bless you for taking time out of what i'm sure is a busy life to help others.i think god has a special heaven for dogs and the people that love them.

Answer
This sounds like a breast tumor.  You should take her to the vet for an examination.  I can not diagnose her over the internet.  If it is indeed a tumor, there is a high possibility that it is cancerous since she is not spayed.   Early detection and treatment of breast cancer is the best for a longer life, just like in women.