Hi,
How are you? What other symptoms are present like fever, fatigue,discharge or pruritus? It could be due to irritation, skin conditions, viral infection and even from ill fitting brassiere. If it persists, you may need to have this checked by your doctor and have diagnostic tests done for proper diagnosis. Take care and do keep us posted.
Could be petechiae, harmless red spots. I don't know of a cancer that presents as red spots