There are many different types of breast cancer. Each is named by that part of the breast where cancer cells begin to grow. Ductal carcinoma is the most common type. It begins in the cells of the ducts. Lobular carcinoma is another type of breast cancer that starts in the lobes or lobules. If a tumor remains within the duct or lobule, it is known as carcinoma in situ; a tumor that spreads outside the duct or lobule is known as infiltrating or invasive carcinoma.
Doctors diagnose and classify breast cancer according to stages (stages 0 through IV). In order to determine the stage of breast cancer, the oncologist considers three important factors: tumor size, nodal status, and metastasis.
Tumor size
The size of the primary tumor is one of the main distinguishing characteristics.
Nodal status
Nodal status indicates the presence or absence of cancer cells in glands or lymph nodes (small bean-shaped organs that make and store cells that fight infection; found in many places in the body, including under the arms, behind the ears and in the groin). Nodal status helps to define the stage of breast cancer.
Metastasis
This term describes cancer that has spread from the affected breast to other areas of the body — soft tissue (such as tissue of the opposite breast, distant lymph nodes, or skin), organs such as the liver or lungs, and bone.
Stage 0
Ductal or lobular carcinoma in situ is very early breast cancer that has not spread beyond the duct or lobule.
Stage I
Tumor is 2 centimeters or smaller and has not spread outside the breast.
Stage IIA
No tumor is found in the breast, but cancer is found in the axillary lymph nodes, OR tumor is 2 centimeters or smaller and has spread to the axillary lymph nodes, OR tumor is 2-5 centimeters but has not spread to the axillary lymph nodes.
Stage IIB
Tumor is 2-5 centimeters and has spread to the axillary lymph nodes OR is larger than 5 centimeters but still confined to the breast.
Stage IIIA
No tumor is found in the breast but has spread to the axillary lymph nodes that are attached to each other or to other structures, OR the tumor is 5 centimeters or smaller and spread to the axillary lymph nodes that are attached to each other or to other structures, OR
the tumor is larger than 5 centimeters and spread to the axillary lymph nodes that may or may not be attached to each other or to other structures.
Stage IIIB
The tumor has spread to tissue near the breast (the skin or chest wall, including the ribs and chest muscles) AND may have spread to lymph nodes within the breast area or under the arm.
Stage IIIC
Tumor has spread to the lymph nodes beneath the collarbone and near the neck, AND may have spread to the lymph nodes within the breast area or under the arm and to the tissues near the breast.1
Stage IV
Tumor has spread to other organs of the body, most often the bones, lungs, liver, or brain.
What Causes Breast Cancer?
The exact cause of breast cancer is unknown. Factors that can increase a woman's risk include heredity, early puberty, late childbearing, obesity, and lifestyle factors such as heavy alcohol consumption and smoking. The biggest risk factor for breast cancer is age — just growing older. Most breast cancers occur in women over the age of 50, and women over 60 are at the highest risk.
A woman's risk for developing breast cancer increases if her mother, sister, daughter, or two or more other close relatives, such as cousins, have a history of breast cancer, especially at a young age. However, 85% of women who develop breast cancer have NO known family history of the disease.
National Cancer Institute Breast Cancer (PDQ®): Treatment. Available at:
http://www.ncis.nih.gov/cancertopics/pdq/treatment/breast/Patient/page2. Accessed January 27, 2005
Stage I
Stage IIB
Stage IIIB
Stage IV