Why would a fibroadenoma require followup magnified mammogram and ultrasound 6 months after diagnosis if can't become malignant?

Better Safe Than...: Rarely, what is presumed to be a fibroadenoma is a sarcoma-like tumor (phyllodes tumor). Therefore, if the tumor is growing on the 6-month follow-up study, excision will be recommended. Remember: common things happen most commonly. Chances are it will not grow and be of no concern.

Was this a: fibroadenoma proven on core biopsy, or a probable fibroadenoma on imaging? If the latter, serial follow up is standard to monitor stability. If the former, the necessity of short interval follow is less clear, but also common. Rarely, a fibroadenoma on core bx path turns out to be a more rapidly growing fibroepithelial variant instead.