red spot on left breast

I have a very large red spot on the top of my left breast with a red line going around the nipple part.  The red spot is about 3 to 4 inches in diameter.  It does not hurt or itch and has no bumps.  It is very smooth.  It looks burised and blood red.  It has continued to grow over the last two days.  There is a knot on the outside of the spot toward the nipple.  It happened overnight and it is really beginning to concern me.  

[Cleveland Clinic]

Dear Tlc1214,  It is difficult to evaluate this over the internet without ability to see.  The skin of the breast is like skin anywhere on the body and is subject to rashes, irritations etc.  If this continues to concern you have it checked out by your doctor.  

[Sai387]

I don't think this will be BC, but I'm not a doctor. What I'm thinking is, in one day the BC will not show and it lookis like you might have some infection. How is your nipple looking. Is it inverted? Are you getting any nipple discharge? Is the Red Patch is like a patch? Do you have any lumps in your breast or under your Arm?

Be Cool, call your PCP and discuss it.