Breast cancer is the second-most-common cancer, and the second-leading cause of cancer deaths, among women. Most breast cancers are slow-growing, but there are types that are aggressive, which is why early detection is essential. Breast cancer is defined by the type of breast cells in which it begins, and is generally categorized as invasive or noninvasive. Breast cancer can also affect men, but it is 100 times more common in women.

Types of Breast Cancer

Two types of cancer that occur rarely are inflammatory breast disease, in which cancerous cells block the lymph vessels within the breast, and Paget disease of the nipple, in which the cells in or around the nipple become cancerous. They account for, respectively, approximately one to six percent, and approximately one percent, of breast cancers. The two most common types of breast cancer are ductal carcinoma and lobular carcinoma. Ductal Carcinoma

This is the most prevalent type of breast cancer, and it begins in the cells that line the milk ducts. More than half of breast cancer cases diagnosed each year are of this type. There are two kinds of ductal carcinoma: Ductal carcinoma in situ (DCIS). With DCIS, cancer cells are found only in the milk-duct lining, and have not spread to other breast tissue. DCIS is often discovered when a mammogram is done as part of a regular screening. In recent years, the number of DCIS diagnoses has increased dramatically, primarily because the number of screening mammograms has increased. DCIS isn\'t life-threatening, but requires treatment to make sure the cancer does not spread.
Invasive ductal carcinoma (IDC)

With IDC, cancer cells have spread from the ducts to other parts of the breast tissue. This is the most common type of invasive breast cancer, requiring treatment at an early stage to make sure it does not spread from the breast tissue to other parts of the body. It accounts for approximately 65 to 85 percent of invasive-type breast cancer cases.

Lobular carcinoma begins in the breast milk-producing glands, which are called lobules. The breast contains 15 to 20 lobes; the lobules are the smaller lobes within them. There are two types of lobular carcinoma: Lobular carcinoma in situ (LCIS) With LCIS, cancer cells are found only in the breast lobules, and do not spread to other tissue. LCIS is asymptomatic, and usually does not show up on mammograms. It is often discovered when a biopsy is performed for another reason. Invasive lobular carcinoma (ILC) With ILC, cancer cells spread from the lobules to close-by breast tissue. It requires treatment at an early stage to make sure it does not spread from the breast to other parts of the body. It accounts for approximately 10 to 15 percent of invasive-type breast cancer cases. Risk Factors for Breast Cancer The greatest risk factor for developing breast cancer is being female, probably because men produce much less estrogen and progesterone, hormones that can promote the growth of malignant breast cells. Other risk factors for women may include: Being 55 years of age or older Carrying a BRCA1 or BRCA2 gene mutation Having a family history of breast cancer Having been diagnosed with breast cancer before Having dense breast tissue Having certain benign breast conditions Using, or having used, hormone therapy Signs or Symptoms of Breast Cancer Women are advised to perform a breast self-exam once a month to check for changes or abnormalities, which may include: A lump in the armpit that does not go away after a menstrual cycle Swelling in the armpit Pain or tenderness in the breast A change in the size, contour, texture or temperature of the breast A change in the nipple An unusual discharge from the nipple A flattening or indentation in the breast Diagnosis of Breast Cancer Most testing for breast cancer begins when a woman or her doctor finds an abnormality in the breast through a physical exam, or when a routine mammogram picks up an abnormality. Tests that may be performed to diagnose breast cancer include:

• Diagnostic mammogram
• Ultrasound
• MRI scan
• Fine-needle-aspiration biopsy
• Core needle biopsy
• Surgical biopsy
• Ductogram
• Sentinel-node (lymph-node) biopsy