I Have Patches Of Brown Skin All Over My Body

I have patches of brown skin all over my body for years. Never goes away and keeps the same shape almost like clouds printed all over my skin and if im hot the patches turn red .the patches never burn out itch. The patches are located on the bend of my arms my neck ,abdomen, groin,belly . would like to know if there is medicine i can take to help or if this is a skinn cancer.i'm willing to take pictures. Thanx