The online medical encyclopedia MedlinePlus reports that many things can cause breast lumps, most of which prove non-cancerous. Breast lumps can appear at any age, and do so for a variety of different reasons. For example, infants may develop a breast lump due to estrogen in breast milk, and adolescent boys may develop breast lumps due to changes in hormones that occur around the time of puberty. Some adult women develop breast lumps for a variety of common causes.
Fibrocystic Changes
MedlinePlus reports that breasts can undergo many changes in the adult woman, especially during the reproductive years. Breasts contain fibrous tissue that can change over time. According to MedlinePlus, doctors may also use the phrase "fibrocystic breast disease," however, they maintain that these changes do not result as part of a disease, but instead describe normal changes in the fibrotic tissue of the breast. These changes can cause the breast to feel painful and lumpy, but do not prove harmful and do not increase a woman's risk of developing breast cancer.
Breast Cysts
The Mayo Clinic reports that cysts can commonly cause a lump to appear in the breast. They describe cysts as fluid-filled sacs, and there may be one or multiple cysts in one or both breasts. According to the Mayo Clinic, the cyst usually feels like a grape or water balloon; occasionally the cyst will feel firm and solid. Cysts are most common in women in their 30s and 40s. The National Cancer institute reports that the cyst may become painful as the woman's period begins. The Mayo Clinic notes that cysts do not require treatment unless the cyst grows very large or becomes very painful. In this case, the heath care provider would drain the cyst of fluid to decrease the woman's pain and the size of the cyst.
Fat Necrosis
The National Cancer Institute reports that fat necrosis can cause the appearance of a lump in the breast. A lump due to fat necrosis usually feels round and firm, and painless. Fat necrosis occurs in response to injury, surgery or radiation therapy.
Fibroadenomas
According to the National Cancer Institute, fibroadenomas are noncancerous round, hard lumps that may feel like a small marble. The lump may move within the breast, and is usually painless. The National Cancer Institute reports that this type of lump proves more common in young women, less than 30 years old.
Breast Cancer
Though less common than the conditions listed above, MedlinePlus reports that another cause of breast lumps in women is breast cancer. These lumps result because of the growth of cancerous cells, meaning normal breast cells have transformed into cells that grow uncontrollably and damage the normal tissue around them. Doctors differentiate breast cancer from the other more common cause of breast lumps by mammogram, ultrasound and biopsy. The characteristics of the lump differ depending on the type of cell that becomes cancerous; other symptoms, such as nipple discharge, may or may not be present.
