Light brown spot in a perfect circle on breast itches no rashes just itch but also have dry skin what could this be?

Itchy spot: A physician or dermatologist would have to inspect this spot in order to advise you. Have it examined if this lesion persists. Dry skin is a cause of itching. In the meantime I see no harm in applying a tiny amount of corticosteroid ointment on it to relieve the itch. Applying a moisturizer to your skin while it's wet after a shower keeps moisture and oils within the skin.