Because I am certainly not breastfeeding and Mastitis is rare otherwise! I went to the ER tonight as my Dr is out of town and I was getting very tender and pink, and sure enough that's what I have. In this instance it has been caused by a staph or strep bacterial infection that's gone through the skin. Last week Callie caught me on this 'boob' with her claws, so that was probably the cause.
So it's antibiotics and painkillers, rest and warm compresses for a few days. If you've ever had it you know how uncomfortable I am, if you haven't then avoid at all costs. Needless to say in this instance no piccies will be posted for added interest!