First, don’t panic — 80 to 85 percent of breast lumps are benign, meaning they are noncancerous, especially in women younger than 40. Not only that, but if you’re of an age to be having regular mammograms, and if those mammograms have been negative, the odds are even better that your palpable (capable of being felt) lump is not cancer. “I tell women that years before they ever experience a palpable lump we will have seen something on their screening mammogram,” says Steven R. Goldstein, MD, an obstetrician and gynecologist and a professor of obstetrics and gynecology at NYU Langone Medical Center in New York City. Even armed with that knowledge, it’s hard not to worry if you find a lump. At the very least, you’ll have questions. 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? RELATED: Speaking Cancer: A Glossary of Formal and Informal Terms Used to Describe Cancer Tests, Treatment, Patients, and More A lump in the breast distinguishes itself from this background of normal irregularities. Harmless breast lumps can be solid and unmovable, like a dried bean; or movable, soft, and fluid-filled — you can roll it between your fingers like a grape. A lump may be pea-size, smaller than a pea, or even several inches across, although this larger size is rare. What typically differentiates a benign breast lump from a cancerous breast lump is movement. That is, a fluid-filled lump that rolls between the fingers is less likely to be cancerous than a hard lump in your breast that feels rooted in place. Another rule of thumb has to do with pain. Breast cancer does not usually cause pain. Benign conditions sometimes do, although there are exceptions to this rule as well. For instance, a rare form of breast cancer, inflammatory breast cancer, may cause symptoms such as aching, tenderness, pain, or burning in the breast. The only way to know the status of a lump for sure is through medical tests, such as an ultrasound, a mammogram, or a fine needle aspiration (FNA), in which your doctor uses a tiny needle to extract a bit of the lump for laboratory examination. Not all benign breast lumps will require additional testing, at least not right away. If you find what appears to be a fluid-filled cyst during your menstrual period, for instance, your doctor may want to check your breast again at the end of your period to see if the cyst has disappeared. If the cyst goes away, you and your doctor will know your lump was indeed benign and related to the hormonal fluctuations associated with menstruation. RELATED: What Is a Skin Lump? Symptoms, Causes, Diagnosis, Treatment, and Prevention Here are some of the most common benign breast conditions. Fibrocystic changes These changes cause a general lumpiness that can be described as “ropy” or “granular,” and affect at least half of all women. Symptoms of fibrocystic change include tender, fibrous, rubbery tissue; a thickening of tissue; or a round, fluid-filled cyst. These changes, which are related to hormonal fluctuation, may increase as you approach middle age and disappear with menopause. Sometimes doctors recommend limiting salt and caffeine consumption to ease fluid buildup. Birth control pills may also ease symptoms. Cysts Cysts are round or oval sacs, often measuring one to two inches across. They may be tender to the touch and filled with fluid. They may come and go with your menstrual period, becoming larger and more tender at the beginning of your period and disappearing at the end. Your doctor may order an ultrasound or a fine needle aspiration to make sure it’s a cyst and not something else. In very rare cases, when a cyst is particularly large or painful, your doctor may use a needle to withdraw and reduce the fluid inside it. Cysts generally affect women between ages 35 and 50. Fibroadenoma These benign lumps occur primarily in young girls and women in their teens and twenties. Fibroadenomas are more common in those who use birth control pills before age 20. They range in size from microscopic to several inches across, are movable under the skin, and are round and hard like a marble. Your doctor may opt to identify it via FNA or biopsy, or removal of the lump. If the fibroadenoma shrinks or doesn’t grow over time, and your doctor is sure of the diagnosis, he or she may decide to simply leave it alone. Fat necrosis This occurs when fatty breast tissue is damaged by injury to the breast, resulting in the formation of round, firm lumps. It’s more common in women with large breasts, particularly in obese women. Your doctor will most likely watch the lump through several menstrual cycles and may decide to remove it surgically. Sometimes the necrosis will produce what is called an oily cyst, which your doctor can drain with a needle. Nipple discharge Sometimes women experience nipple discharge with or without a breast lump. The color of nipple discharge can vary from yellow to green. A clear to milky discharge may mean a hormonal malfunction. Greenish black discharge could be related to duct ectasia, a narrowing or blockage of the duct. A bloody discharge can mean cancer but is more likely to be due to injury, infection, or a benign tumor. Your doctor may study the fluid under a microscope to determine the problem. Mastitis An infection of the milk duct, mastitis can create a lumpy, red, and warm breast, accompanied by fever. It occurs most commonly in women who are breastfeeding, but can occur in non-breastfeeding women as well. Treatment involves warm compresses and antibiotics. Because these symptoms are similar to inflammatory breast cancer, if they occur in a non-breastfeeding woman a doctor may want to do a biopsy. Other, less-common conditions Some medical conditions cause breast lumps, including hyperplasia, which is an overgrowth of cells in the breast ducts or lobules; adenosis, which causes enlarged lobules; intraductal papilloma, a wart-like growth of gland tissue that grows in the duct; and lipoma, which is a benign fatty tumor. RELATED: Real Stories From Women With Metastatic Breast Cancer

Signs of Cancerous Breast Tumors

Though most breast lumps are benign, some do turn out to be cancerous. If a tumor is cancerous, it will continue to grow and invade normal nearby tissue. If it isn’t treated, it can spread to other areas in the body. Most cancerous breast tumors first appear as single, hard lumps or thickening under the skin. Other signs to watch for include a change in nipple appearance, nipple secretions, nipple tenderness, and a dimpling or puckering of the skin. About half of cancerous breast lumps appear in the upper, outer quadrant of the breast, extending into the armpit. About 18 percent of breast cancer tumors show up in the nipple area. Around 11 percent are found in the lower quadrant, and 6 percent are located in the lower, inner quadrant. RELATED: What Is an Ovarian Cyst? Symptoms, Causes, Diagnosis, Treatment, and Prevention

If You Find a Breast Lump

Most benign breast conditions are treatable, and some will even go away on their own, but it’s best to let your doctor be the one to tell you that. All breast lumps should be evaluated by a medical professional, who will help you decide how to proceed. Because of the fluctuations in breast tissue that occur in response to hormonal changes throughout the month, it’s typically a good idea to do a self-exam at the same point every month, such as a few days after the end of your menstrual cycle. Additional reporting by Julie Marks.