When is a Rash Cancer?

Hope this is the right section, I just have questions to try to make myself understand some things better perhaps.

Is there an easy way to tell if a rash is cancer? I have a rash on the aereola (though mine are rather large...) Though I think it may be from the heat. (There's heat rash under my boobs X.X)

How many days should I wait to see if it goes away? Does a cancerous rash "go away"? (IE: Turn back to skin color and not be red, I guess.)

Some things I read that may or may not be true in my Online searching: Breast is warm to the touch and Breast pain (from a constant ache to stabbing pains)

Aren't they always warm? And what sort of breast pain? I think I feel occasional aches and spikey things, but could that just be from whatever the rash is?) Both of my boobs are warm, but I figure that's just normal body temp?

Also reading http://www.mayoclinic.com/health/pagets-disease-of-the-breast/DS00771

It sounds like the rash for Paget's starts on the nipple and goes from there? I'm 24 so I guess it's probably not that.

I just really hate how I've become so easily paniced by any little thing, breast or otherwise related....

Thanks for any help you guys may provide.

[SkieMyu]

Hrm, this got moved. My post is mainly referring to breast cancer.