Two of the most common causes of benign single breast lumps are cysts and fibroadenomas. There are also several other conditions that can present themselves as lumps, such as fat necrosis and sclerosing adenosis.
A cyst is a fluid-filled sac that develops in the breast tissue and is most common in women approaching menopause. They often enlarge and become tender and painful just before the menstrual period, and may seem to appear overnight. Cysts are rarely malignant (cancerous) and may be caused by a blockage of breast glands.
Cysts can feel either soft or hard. When close to the surface of the breast, cysts can feel like a large blister, smooth on the outside, but fluid-filled on the inside. However, when they are deeply imbedded in breast tissue, a cyst will feel like a hard lump because is covered with tissue.
Your doctor may identify a lump as a cyst by physical exam, but many doctors confirm the diagnosis by mammography or ultrasound exam. The doctor may then perform a fine-needle aspiration as the next step in diagnosing the cyst. This procedure involves guiding a very thin needle into the cyst and drawing fluid from it. This procedure also serves as the treatment for this condition, as once the cyst is aspirated, it collapses and disappears. Cysts can reappear at a later date, in which case they are simply drained again.
Fibroadenomas are solid, smooth, firm, benign lumps that are most commonly found in women in their 20s and 30s. They are the most common benign lumps that occur in women and can occur in women of any age. Increasingly, they are being seen in postmenopausal women who are taking hormone therapy.
The painless lump feels rubbery, moves around freely, and very often is found by the woman herself. Fibroadenomas vary in size and can grow anywhere in the breast tissue.
While most doctors can recognize this type of lump simply by feeling it, generally, the diagnosis is confirmed by mammography or ultrasound and fine-needle aspiration. Sometimes, in very young women, the fibroadenoma is not removed. However, since sometimes these tumors enlarge with pregnancy and breastfeeding, doctors may recommend surgically removing the fibroadenoma.
While fibroadenoma does not lead to cancer, there is a type of fibroadenoma that has been associated with a slightly increased risk of cancer, particularly in women with a family history of the disease.
Fat necrosis is a condition in which painless, round, firm lumps caused by damaged and disintegrating fatty tissues form in the breast tissue. Fat necrosis often occurs in women with very large breasts or in response to a bruise or blow to the breast. This condition may also be the result of a lumpectomy and radiation from a previous cancerous lump. In some cases, doctors will watch the lump through several menstrual cycles, and may perform a mammogram before deciding whether or not to remove it. These lumps are not malignant and there is no reason to believe that they increase a woman's risk of cancer.
Sclerosing adenosis is a breast condition that involves excessive growth of tissues in the breast's lobules, often resulting in breast pain. While these changes in the breast tissue are microscopic, they may show up on mammograms as calcifications and can produce lumps. Usually a biopsy is necessary to distinguish this condition from cancer. In addition, because the condition can be mistaken for cancer, the lumps are usually removed through surgical biopsy. Some studies have found that women with sclerosing adenosis have a slightly increased risk of breast cancer.