Had ultrasound for a rash on 1 breast. no lumps but thickening of the skin under the rash inside the breast. what does this mean exactly?

There is no skin: ...inside the breast itself, so I can understand why you're confused. If the rash affects all the layers of the skin, it can cause thickening of the skin under the rash but outside of the breast tissue. If you haven't had a mammogram, you should get one. Altho breast cancer is rate at your age, you may need a biopsy to be sure that the thickening is confined to the skin. Dr. Anne.