Types of Breast Cancer

The main parts of the female breast are lobules (milk-producing glands), ducts (milk passages that connect the lobules and the nipple), and stroma (fatty tissue and ligaments surrounding the ducts and lobules, blood vessels, and lymphatic vessels) (Figure 1).

Lymphatic vessels are similar to veins, but carry lymph instead of blood.

Lymph is a clear fluid that contains tissue waste products and immune system cells. Most lymphatic vessels of the breast lead to axillary (underarm) lymph nodes. Cancer cells may enter lymph vessels and spread out along these vessels to reach lymph nodes.

Lymph nodes are small, bean-shaped collections of immune system cells important in fighting infections. When breast cancer cells reach the axillary lymph nodes, they can continue to grow, often causing swelling of the lymph nodes in the armpit.

If breast cancer cells have multiplied in the axillary lymph nodes, there is a chance that they may have spread to other parts of the body.

Carcinoma in Situ

In situ means that the cancer stays confined to ducts or lobules and has not invaded surrounding fatty tissues in the breast or spread to other organs in the body. There are two types of breast carcinoma in situ:

Lobular carcinoma in situ (LCIS): Also called lobular neoplasia. It begins in the lobules, but does not penetrate 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 slightly higher risk of developing a cancer in either breast in the future.

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.

Starting in a milk passage, or duct, of the breast, this cancer breaks through the wall of the duct and invades the breast’s fatty tissue. It can spread to other parts of the body through the lymphatic system and through the bloodstream. Infiltrating or invasive ductal carcinoma accounts for about 80 percent of all breast cancers.

Infiltrating (or invasive) Lobular Carcinoma (ILC)

This type of cancer starts in the milk-producing glands. About 10 to 15 percent of invasive breast cancers are invasive lobular carcinomas.

Medullary Carcinoma

This type of invasive breast cancer has a relatively well-defined distinct boundary between tumour tissue and normal breast tissue. It accounts for about 5 percent of all breast cancers. The prognosis for medullary carcinoma is better than that for invasive lobular or invasive ductal cancer.

Colloid Carcinoma

This rare type of invasive disease, also called mucinous carcinoma, is formed by mucus-producing cancer cells. Prognosis for colloid carcinoma is better than for invasive lobular or invasive ductal cancer.

Tubular Carcinoma

Accounting for about two percent of all breast cancers, tubular carcinomas are a special type of invasive breast carcinoma. They have a better prognosis than invasive ductal or lobular carcinomas and are often detected through breast screening.

Adenoid Cystic Carcinoma

This type of cancer rarely develops in the breast; it is more usually found in the salivary glands. Adenoid cystic carcinomas of the breast have a better prognosis than invasive lobular or ductal carcinoma.

Pathology Review

Because results of the biopsy so profoundly affect the treatment a woman will receive, the NSW Breast Cancer Institute guidelines recommends you get a second opinion, called a pathology review. This is sometimes necessary – but particularly for low-grade DCIS and for rare tumours and sometimes for patients with node-negative breast cancer if the grade of the tumour determines treatment.