Laura
I would highly suggest you consult your physician, if for no other reason, than to rule out breast cancer that may have spread to the lymph nodes. It is more likely to be something like a swollen sweat gland, which may be irritated by a perfume in your deodorant. Try changing brands to a perfume free brand, but still get it checked out. The sooner the better, just for your own piece of mind. Always keep in mind, breast cancer affects both sexes, male and female.