Hi,
Skin on the breast and areola is like skin anywhere else on the body and is subject to many common abnormalities. In my opinion, it sounds more like a skin issue rather than a breast problem.
A variety of skin conditions could be responsible for this... such as hormonal changes, seborrheic keratoses, allergic reaction and sometime the cause is unknown. I don't think you should be worried about breast cancer, but since it's always better to make sure, I would recommend that you see a dermatologist who should be able to help sort this out for you.
All the best..