Paget's disease of the breast is a rare form of breast cancer, accounting for less than 5 percent of all breast cancers. Paget's disease of the breast starts in the breast ducts and extends to the skin of the nipple and to the dark circle of skin (areola) around the nipple. Paget's disease of the breast isn't related to Paget's disease of the bone, a metabolic bone disease.

Paget's disease of the breast occurs most often in women over age 50. Most women with Paget's disease of the breast have underlying infiltrating ductal breast cancer. Only in rare cases is the cancer confined to the nipple itself.

Paget's disease of the breast affects your nipple and its surrounding skin (areola). It's easy to mistake the signs and symptoms for skin irritation (dermatitis) or another noncancerous (benign) skin condition of the nipple. In the early stages of the disease, you might notice only some flaky or scaly skin on your nipple, accompanied by slight itching or redness. These skin changes can come and go, making it appear as if your skin is healing on its own. On average, a woman may experience signs and symptoms for six to eight months before a diagnosis of Paget's disease of the breast is made.

When Paget's disease progresses, a patch of scaly, hardened skin resembling eczema develops on the nipple, areola or both. The area of affected skin may spread beyond your nipple and areola. The scaly skin might ooze or become crusty. Other possible signs and symptoms include:

• Redness
• Itching
• Tingling
• A burning sensation
• Skin thickening
• A flattened or inverted nipple

Some women with Paget's disease have straw-colored or bloody nipple discharge. You may or may not be able to feel a distinct lump underneath your nipple and areola.

Usually, the skin and nipple changes associated with Paget's disease occur in only one breast. But in some cases, Paget's disease affects both breasts.

Doctors don't know what causes Paget's disease of the breast. But one widely accepted theory is that Paget's disease of the breast results from an underlying ductal or invasive breast cancer. Cancer cells from the original tumor travel through milk ducts to the nipple and its surrounding skin (areola).

Another theory suggests that normal cells on the surface of your nipple spontaneously transform into cancer cells. In rare cases of Paget's disease, no underlying breast cancer can be found.

Risk factors that affect your likelihood of developing Paget's disease are the same factors that affect your risk of developing any other type of breast cancer.

Some factors that make you more susceptible to breast cancer include:

• Aging. Your chances of developing breast cancer increase as you get older.
• A personal history of breast cancer. If you've had breast cancer in one breast, you have an increased risk of developing cancer in the other breast.
• Family history. If you have a mother, sister or daughter with breast or ovarian cancer or both, or even a male relative with breast cancer, you have a greater chance of also developing breast cancer.
• Genetic predisposition. Defects in one of several genes, especially BRCA1 or BRCA2, put you at greater risk of developing breast cancer as well as ovarian and colon cancers.
• Radiation exposure. If you received radiation treatments to your chest as a child or young adult, you're more likely to develop breast cancer later in life.
• Excess weight. Weighing more than is healthy for your age and height increases your risk of breast cancer — especially if you gain that weight after menopause. Also, significant weight gain during puberty is linked to increased risk of breast cancer later in life.
• Exposure to estrogen. The longer you're exposed to estrogen — which circulates in higher levels in your body from menstruation to menopause — the greater your breast cancer risk. Early menstruation, occurring before age 12, or late menopause, occurring after age 55, prolongs your exposure to estrogen. Taking estrogen, such as for hormone replacement therapy, also increases the risk of breast cancer for some women.
• Race. White women are more likely to develop breast cancer than black or Hispanic women are, but black women are more likely to die of the disease.

Having one or more risk factors doesn't necessarily mean you'll develop breast cancer. Most women with breast cancer have no known risk factors.

Early detection of Paget's disease of the breast is important. Regular screening mammograms and breast self-exams may help catch the breast cancer in its earliest possible stage. As part of your breast self-exam, always check the nipple and areola — the area of dark skin around the nipple — on both breasts. If you feel a lump or see skin irritation in this area that persists for more than a month, see your doctor.

If you're being treated for a skin lesion on your breast, such as eczema, and you notice that skin condition doesn't resolve with treatment, make a follow-up appointment with your doctor. You may need a biopsy of the affected area — your doctor takes a small tissue sample for microscopic evaluation — to look for Paget's disease of the breast.

Your doctor performs a physical exam, noting the appearance of the skin on and around your nipples and feeling for any lumps or unusual areas in your breasts. You may undergo mammography or other imaging tests to check for an underlying breast cancer.

Your doctor may remove a small tissue sample (biopsy) from the skin of your nipple for examination under a microscope. If you have nipple discharge, a sample of the discharge might also be collected for microscopic examination. Specialists examine these tissue samples for the presence of cancerous cells that indicate Paget's disease of the breast. If cancer cells are found in the samples collected, you may be referred to a breast surgeon to discuss your treatment options.

Paget's disease of the breast usually requires surgery. Which type of surgery you need depends on the condition of the skin around your nipple and how advanced the underlying cancer is.

Surgical options include:

• Simple mastectomy. This procedure involves removing your breast, but not the lymph nodes in your armpit (axillary lymph nodes). Simple mastectomy is recommended in cases in which an underlying breast cancer exists but it isn't invasive breast cancer and it hasn't spread to the lymph nodes.
• Skin-sparing mastectomy. In this procedure, the surgeon makes an incision around your nipple and areola, removes all of the underlying breast tissue, but preserves the overlying skin. Breast reconstruction with breast implants or with your body's own tissue (autologous reconstruction) is usually performed during the same surgery. Skin-sparing mastectomy isn't an option if the skin changes associated with Paget's disease have spread beyond your areola.
• Modified radical mastectomy. A modified radical mastectomy is generally recommended if you have invasive breast cancer or extensive in situ breast cancer with spread to the lymph nodes in your armpit. In this procedure, the surgeon removes the breast, the lining of the chest wall muscle and some of your underarm (axillary) lymph nodes. The lymph nodes are checked for signs that the cancer has spread (metastasized).
• Lumpectomy. Lumpectomy is a breast-conserving procedure in which the surgeon removes only the diseased portion of your breast. This procedure is generally considered if you have Paget's disease of the breast but no other evidence of underlying breast cancer. Your surgeon makes an incision around your areola, removing it and your nipple along with a wedge- or cone-shaped section of your breast. The surgeon focuses on removing as little breast tissue as possible, while ensuring that the tissue removed includes an outer margin of normal cells so that only healthy cells remain. Lumpectomy to treat Paget's disease of the breast almost always requires follow-up radiation therapy as adjuvant treatment. Lumpectomy wouldn't be recommended if you can't have radiation therapy for some reason. Nipple reconstruction may be an option after your treatment.

After your surgery, your doctor may recommend additional treatment (adjuvant therapy) with anti-cancer drugs or hormone therapy to prevent a recurrence of your breast cancer. This depends on the extent of your breast cancer and whether the tumor tests positive for certain characteristics, such as having estrogen or progesterone receptors.

You can't avoid certain risk factors for breast cancer, such as your age, genetics or family history. But other factors that could increase your chances of developing breast cancer are well within your control. Healthy lifestyle habits, such as getting enough exercise, limiting alcohol and eating right, may offer you some protection from breast cancer.