What causes broken blood vessels on breast?

Trauma ?: The most likely cause is trauma. It is best to see a doctor about this especially if you dont remember anything bumping or bruising it.

Normal.: The prominence of veins through the skin is affected by many factors including levels of hydration and dehydration, body temperature as well as outside temperature, medications and even levels of stress. Fair skinned people tend to have more easily visible veins than darker individuals and hereditary plays a strong role also. In a healthy person, visible veins are usually not of any concern.