What is a fibroadenoma of the breast and is it dangerous? Can it become cancerous?

Benign. Fibroadenomas are a benign tumor of the breast. Chances of them becoming a malignant ( cancerous ) tumor are very rare. They are usually identified as a palpable lump that is sometimes tender. If the pain is tolerable with Ibuprofen they do not need too be removed. A needle biopsy can confirm the diagnosis. You should then discuss risks and benefits of removal and leaving it with surgeon.
Not danerous. Fibroadenoma is a benign breast lump (not cancerous). It does not turn into cancer. Its additional risk for breast cancer is minimally more than average but it is not considered high risk for breast cancer. Small fibroadenomas can be safely observed and monitored. If a fibroadenoma grows larger and changes overtime its removal may be needed. Check with a breast care specialist.