The clinical stage of breast cancer is the best indication of the likely outcome. Common causes Some of the causes of lumps in a mature woman's breast are discussed below. Fibrocystic changes can occur in either or both breasts and is most common in the upper outer quadrants. Fibrocystic change is basically an exaggeration of normal breast architecture. There is variable enlargement of some of the milk glands and a thickening of the fibrous tissue that supports the glands and gives the breast its shape.
Fibroadenomas are the most common tumors found in women's breasts.
They occur most often during the reproductive years. They usually have a rubbery feel, are fairly movable within the breast tissue, and may feel more prominent over a rib. They are not tender and usually do not become malignant. Most often, there is fibrocystic change as well. In some cases fibroadenomas can show changes that are suggestive of increased risk of breast cancer in the future.