Breast Lumps: What's Normal, What's Not So you found a lump -- now what? Though all breast lumps need to be evaluated by a trained medical professional, the majority turn out to be noncancerous, especially in younger women. First, don't panic... Like what you're reading? Then LIKE us on Facebook! 80 to 85 percent of breast lumps are benign, meaning they are noncancerous, especially in women younger than age 40. Not only that, but if you're at an age where you've been having regular mammograms, and if those mammograms have been negative, odds are even better that your palpable (capable of being felt) lump is not cancer. But how do you know? How do you differentiate between a lump that is breast cancer and one that is benign? What causes benign breast lumps? And do they go away on their own? Breast Lumps Distinctions Your breasts are made up of fat, nerves, blood vessels, fibrous connective tissue, and glandular tissue, as well as an intricate milk-producing system of lobules (where the milk is made) and ducts (the thin tubes that carry milk to the nipple). This anatomy in and of itself creates a lumpy, uneven terrain.