A fibroadenoma is a benign (not cancerous) breast lump that is common in young women, often appearing between the ages of 15 and 35. It is a solid mass that is usually round or oval with clear borders, and it can be as small as a pea or as large as a golf ball. Fibroadenomas are usually painless, firm, smooth, and rubbery to the touch, and they can move easily within the breast tissue. They are made up of both glandular tissue and stromal (connective) tissue. Fibroadenomas can be diagnosed through a breast examination, ultrasound, or biopsy. While most fibroadenomas are harmless and do not require treatment, some may need to be monitored for changes in size or feel, or removed through surgery if they are large, complex, or causing discomfort.