A fibroadenoma is a non-cancerous (benign) breast tumor that feels like a firm, round, and movable lump. They are composed of both fibrous and glandular tissue and are most common in women between the ages of 15 and 35, though they can occur at any age. Symptoms are often minimal, but they may cause pain, grow larger during pregnancy, or shrink after menopause. While often harmless and sometimes requiring no treatment, diagnosis involves a physical exam, ultrasound, and possibly a biopsy.