[Jan & the M&M's]

My Mollie is a 7 year old yorkie, a retired breeder dog, i got her last year from my breeder, immediately had her spayed. She's been wonderful, no health problems, tonight I noticed a large lump on her chest - mid chest, between her nipples. I gave her a bath three days ago, there was no lump. It seems larger this evening than when I first noticed it this afternoon. It doesn't hurt her, but it's the size of my thumb pad, firm and seems to be palpable. Of course I'm in a panic. Anybody have any thoughts on this?

I gave her Advantix a couple of days ago for the first time. Could Advantix cause this lump? Oh, I hope it's not breast cancer, I'm really panicked.

Thanks for any help you can give me.