Itchiness of the breast is not usually due to cancer. It is usually due to other conditions that can affect the breast such as eczema or mastitis.
There is a condition that affects the nipple (called Paget's Disease) that can cause itching.
This condition develops in the nipple or the darker area of skin around it (the areola). It usually first appears as a red, scaly rash of the skin that may look like eczema. There might also be some discharge or bleeding from the nipple.
With Paget’s disease there might be breast cancer in the tissues behind the nipple. Or there might be carcinoma in situ. This means that there are cancer cells but they are completely contained within the lining of the breast ducts.
There is a type of breast cancer called inflammatory breast cancer that can cause skin changes on your breast. With this type of cancer, the breast or part of the breast can become red, inflamed, painful and swollen.