Here's something for you..when we where kid's we had a staffie bitch.. in the late 70's she died from a mammary tumor we also had a collie mongrel she died in the late 80's from a mammary tumour that went to her brain.. i lost a terrier bitch around 5yr's ago at 8 yr old after countless operation's to remove mammary tumour's after it spread to her brain..my brother had a staffie x sharpei put to sleep at the beggining of the year..but prior to that she had a opperation for a womb infection and also a big mammary tumour..which finaly spread to it's brain yet again..