A noncancerous breast tumor that most often occurs in young women. Reproductive hormones may cause fibroadenomas. A fibroadenoma feels like a firm, smooth, or rubbery lump in the breast with a well-defined shape. It's painless and moves easily when touched. Although healthy breast tissue often feels lumpy, a new lump or change in the breasts should be looked at by a doctor. Treatment may include monitoring for changes in the size or feel, a biopsy to evaluate it, or surgery to remove it.