Breast cancer is an abnormal growth of cells that line the ducts and the lobules. Breast cancer is classified by whether the cancer started in the ducts or the lobules, whether the cells have “invaded” (grown or spread) through the duct or lobule, and the way the cancer cells look under a microscope.
Non-Invasive Breast Cancer
Carcinoma in Situ
In situ means that the cancer is still in the ducts or lobules where it started and has not spread into surrounding fatty tissues in the breast or to other organs in the body. There are 2 types of breast carcinoma in situ:
- Lobular carcinoma in situ (LCIS):
Also called lobular neoplasia. It begins in the lobules, but does not grow through the lobule walls. Most breast cancer specialists think that LCIS, itself, does not usually become an invasive cancer, but women with this condition do run a higher risk of developing an invasive cancer in either breast.
- Ductal carcinoma in situ (DCIS):
The most common type of noninvasive breast cancer. Cancer cells inside the ducts do not spread through the walls of the ducts into the fatty tissue of the breast. These are treated with surgery and sometimes radiation, which are usually curative. Having untreated DCIS greatly increases the risk of invasive breast cancer.
Invasive Breast Cancer
- Infiltrating (or Invasive) Ductal Carcinoma
The cancer starts in a milk passage, or duct, of the breast, but then the cancer cells break through the wall of the duct and spread into the breast’s fatty tissue. They can then invade lymphatic channels or blood vessels of the breast and spread to other parts of the body. About 80% of all breast cancers are infiltrating or invasive ductal carcinoma.
- Infiltrating (or Invasive) Lobular Carcinoma (ILC)
This type of cancer starts in the milk-producing glands. Like infiltrating ductal breast cancer, this cancer can spread beyond the breast to other parts of the body. About 10% to 15% of invasive breast cancers are invasive lobular carcinomas.
- Medullary Carcinoma
This special type of infiltrating ductal cancer has a relatively well-defined, distinct boundary between tumor tissue and normal breast tissue. It also has a number of other special features, including the large size of the cancer cells and the presence of immune system cells at the edges of the tumor. It accounts for about 5% of all breast cancers.
- Colloid Carcinoma
This rare type of invasive ductal breast cancer, also called mucinous carcinoma, is formed by mucus-producing cancer cells. Colloid carcinoma has a slightly better prognosis and a slightly lower chance of metastasis than invasive lobular or invasive ductal cancers of the same size.
- Tubular Carcinoma
Tubular carcinoma is a special type of infiltrating ductal breast carcinoma. About 2% of all breast cancers are tubular carcinomas. Women with this type of breast cancer have a better outlook because the cancer is less likely to spread outside the breast than invasive lobular or invasive ductal cancers of the same size.
- Inflammatory Breast Cancer
This uncommon type of invasive breast cancer accounts for about 1-3% of all breast cancers. The skin of the affected breast is red, feels warm, and has the appearance of an orange peel. Doctors now know that these changes are not caused by inflammation, but by cancer cells blocking lymph vessels in the skin.
Inflammatory breast cancer has a higher chance of spreading and a worse prognosis than typical invasive ductal or lobular cancers. Inflammatory breast cancer is always staged as stage IIIB unless it has already spread to other organs at the time of diagnosis which would then make it stage IV.