Which is the percent of probability than a breast cyst change in cancer? thanks

Very little to none: Fibrocystic disease is very common in young woman , itself is not premalignant , but has slightly higher incidence of cancer , cyst itself will not turn to cancer

Depends: This is hard to answer without examining you and looking at a breast ultrasound. I recommend you find a breast specialist in your area who can help you answer this question definitively. In general breast cancer is more common in older women.