Case 17

Explanation: Fibroadenoma, a benign fibroepithelial lesion, is the most common breast mass in the pediatric population. Juvenile fibroadenoma, also known as giant fibroadenoma, is a variant characterized by rapid growth to a size of 5 cm or larger. Like normal fibroadenomas, they are usually circumscribed round or oval masses. Biopsy is usually indicated because the potentially malignant Phyllodes tumor can have an identical imaging appearance. Because of their rapid growth and their potential to cause local deformity, they are usually treated with surgical excision.

The other answer choices are possible pediatric breast masses, but are not as common as fibroadenoma.