Breast Cancer

Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast. It is the most common cancer (excluding skin cancer) and the second leading cause of cancer-related death in women in the United States.

Anatomy

Each breast contains 15 to 20 sections called lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can produce milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts. The fat that covers the lobes gives the breast its size and shape.

Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. Lymph vessels lead to organs called lymph nodes. Lymph nodes are small bean-shaped structures that are found throughout the body. They filter substances in lymph and help fight infection and disease. Clusters of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.

The breast is responsive to a complex interplay of hormones that cause the tissue to develop, enlarge and produce milk. The three major hormones affecting the breast are estrogen, progesterone and prolactin, which cause glandular tissue in the breast and the uterus to change during the menstrual cycle.

Types of Breast Cancer

The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular carcinoma and is more often found in both breasts than are other types of breast cancer. 

Less common types of breast cancer include the following:

• Inflammatory breast cancer (diffuse brawny infiltration; breast appears red or inflamed; tends to spread quickly)
• Medullary carcinoma (originates in central breast tissue)
• Mucinous carcinoma (invasive; usually occurs in postmenopausal women)
• Paget disease of the nipple (originates in the milk ducts and spreads to the skin of the nipples or areola)
• Phyllodes tumor (tumor with a leaf-like appearance that extends into the ducts; rarely metastasizes)
• Tubular carcinoma (small tumor that is often undetectable by palpation)

Symptoms and Diagnosis

The earliest sign of breast cancer is an abnormality that shows up on a mammogram before it can be felt by the woman or her health care provider. When breast cancer has grown to the point where physical signs and symptoms exist, a breast lump, or tenderness; skin irritation or dimpling; and nipple discharge and/or pain, scaliness, ulceration, or retraction may be noticed. Breast pain is commonly due to benign conditions and is not usually the first symptom of breast cancer. 

To diagnose breast cancer, the following tests and procedures may be used:

• Mammogram: An x-ray of the breast.
• Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. If a lump in the breast is found, the doctor may need to cut out a small piece of the lump. Four types of biopsies are as follows:
  • Excisional biopsy: The removal of an entire lump or suspicious tissue.
  • Incisional biopsy: The removal of part of a lump or suspicious tissue.
  • Core biopsy: The removal of part of a lump or suspicious tissue using a wide needle.
  • Needle biopsy or fine-needle aspiration biopsy: The removal of part of a lump, suspicious tissue, or fluid, using a thin needle.
• Estrogen and progesterone receptor test: A test to measure the amount of estrogen and progesterone (hormones) receptors in cancer tissue. If cancer is found in the breast, tissue from the tumor is examined in the laboratory to find out whether estrogen and progesterone could affect the way cancer grows. The test results show whether hormone therapy may stop the cancer from growing.

Causes

All cancers are caused by dysfunctions of proteins involved in cell division, apoptosis, or DNA repair (see general characteristics). Dysfunctional proteins may arise from gene mutations or protein interactions with environments. Two genes, BRCA1 and BRCA2, are known to be associated with breast cancer (more info). The following risk factors may increase the chance of developing breast cancer:

• Older age.
• Menstruating at an early age.
• Older age at first birth or never having given birth.
• A personal history of breast cancer or benign (noncancer) breast disease.
• A mother or sister with breast cancer.
• Treatment with radiation therapy to the breast/chest.
• Breast tissue that is dense on a mammogram.
• Taking hormones such as estrogen and progesterone.
• Drinking alcoholic beverages.
• Being white.

Reference:

National Cancer Institute, USA.