While it is rare, malignant transformations of fibroadenomas of the breast have been documented in medical literature. Risk factors include a strong family history of breast/ovarian cancer and BRCA gene mutations. I refer to the articles below for your perusing.
Article Carcinoma developing in a fibroadenoma in a woman with a fam...
Article: Multiple fibroadenomas harbouring carcinoma in situ in a woman with a family history of breast/ovarian cancer (https://jcp.bmj.com/content/55/10/795)
Fibroadenoma is a benign breast disease. This can increase your risk of breast cancer but it still remains low. Evaluating the brest density and family history is equally or more important
Fibroadenoma has been known to be a benign (non-cancerous ) growth. But then it could be fertile soil for malignant growth under some favorable microenvironment