Although Inflammatory breast cancer (IBC) and Paget's disease of the breast are two forms of breast cancer that may include itching as a symptom, it is unlikely a be a symptom of cancer. IBC is associated with other symptoms such as inverted nipple, soreness, swelling or sudden enlargement, aching, swollen lymph nodes under the arm, etc. Paget's usually has the rash around the nipples. You need to see a dermatologist and have a skin biopsy done. This is likely caused from an allergic reaction and it could be a new soap, cosmetic or a new bra. Formaldehyde is often used as a fabric finisher and is considered a probable human carcinogen by the EPA and is also a known allergen. If you stop and think about it you may have purchased a new bra recently or perhaps even switched laundry detergents.