Invasive Breast Cancer

Breast cancer becomes infiltrating or invasive when the cancer penetrates the membrane that surrounds the lobules or ducts. Invasive breast cancer can grow into the supporting tissue between the ducts, blood vessels, lymph nodes and other structures within the breasts. Because of this type of growth with infiltrating breast cancer, there is more of a chance that the cancer will metastasize, spreading from one site to other parts of the body. Most common types of invasive breast cancers include ductal, lobular, tubular, medullary and mucinous.

Infiltrating ductal carcinoma starts in the duct and may break through the wall of the duct to the fatty tissue surrounding the breast. As the cancer invades the duct, a fibrous scar-like tissue is formed. This scar formation may make the ductal carcinoma appear larger than it really is. According to the American Cancer Society, about 80 percent of all breast cancers are infiltrating or invasive ductal carcinoma.

Infiltrating lobular carcinoma starts in the milk-producing glands. This type of cancer may not appear as a distinct lump, but more like an irregular thickening in the breast. About 10 to 15 percent of invasive breast cancers are invasive lobular carcinomas as indicated by the American Cancer Society.

Inflammatory Breast Cancer (IBC) is the fastest-growing and most difficult type of breast cancer to treat. Usually there is no single lump or tumor. Instead, IBC makes the skin of the breast look red and feel warm and gives the skin a thick, pitted appearance that looks a lot like an orange peel. The affected breast may become larger or firmer, tender or itchy. Inflammatory breast cancer is often mistaken for infection (mastitis) in its early stages. Because there is no defined lump, it may not appear on a mammogram, which may make it even harder to detect early. According to the American Cancer Society, this uncommon type of invasive breast cancer accounts for about one to three percent of all breast cancers.

For more information on IBC visit the IBC Fact Sheet from the National Cancer Institute.

Medullary carcinoma is a special type of infiltrating ductal cancer due to the fact that there is a relatively defined and distinct boundary between tumor tissue and normal breast tissue. Other special characteristics of this form of breast cancer are the presence of immune system cells at the edges of the tumor and the large size of the cancer cells. This category of cancer accounts for about five percent of all breast cancers according to the American Cancer Society.  

Mucinous carcinoma is also called colloid carcinoma. It is a rare type of invasive ductal breast cancer, formed by mucus-producing cancer cells. This form of cancer has a slightly better prognosis and a slightly lower chance of metastasis than invading lobular or ductal cancers of the same size.

Tubular carcinoma is a special type of infiltrating ductal breast carcinoma. It is a slow-growing, tube-shaped cancer. The American Cancer Society states about two percent of all breast cancers are tubular carcinomas. Individuals with this type of cancer usually have a slightly better prognosis and the chance of metastasis is slightly lower than invasive lobular or ductal cancers of the same size.