As part of a breast cancer diagnosis, there are other tests run on the tissue sample that will help the oncologist with making decisions about the best treatment plan. Your specific type of breast cancer will be established based on several factors. This is different from the stage of cancer and the hormone receptor status.
Common Categories of Breast Cancer
Most breast cancers are categorized as carcinomas. These tumors start in the cells that line organs and tissues in the body. When carcinomas start in the breast they’re specifically called an adenocarcinoma. Adenocarcinomas start in the milk ducts or the lobules that produce milk.
In addition to determining the point of origin within the breast (ducts or milk glands), breast cancer is also determined to be invasive or noninvasive. This is based on whether the cancer cells have spread outside of the point of origin.
- Noninvasive (in situ) means that the cancerous cells are still confined to their point of origin.
- Invasive (infiltrating) means that cancer has spread to surrounding tissues.
In some cases a noninvasive diagnosis indicates that you may be at a higher risk of developing breast cancer later.
Ductal carcinoma in situ
Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer contained in the lining of the breast milk duct. This is sometimes referred to as Stage 0 because it is not considered life-threatening, but it can increase the risk of developing an invasive breast cancer later on. Most recurrences happen within 5-10 years after initial diagnosis.
Lobular carcinoma in situ
Lobular carcinoma in situ (LCIS) is also sometimes called lobular neoplasia or intralobular. Though the name can be confusing, LCIS is actually not considered cancer or a pre-cancer because it doesn’t turn into invasive cancer if untreated. Rather, LCIS is an indication that a person is at a higher risk of getting breast cancer later on.
Invasive carcinomas tend to be more common for breast cancer patients.
Invasive ductal carcinoma
Invasive ductal carcinoma, or infiltrating ductal carcinoma (IDC), means that abnormal cells that originated in the lining of the breast’s milk duct have invaded surrounding tissue. Over time, IDC can spread to the lymph nodes and possibly to other areas of the body. Invasive ductal carcinoma is the most common type of breast cancer, accounting for approximately 80% of all breast cancers.
Invasive lobular carcinoma
Invasive lobular carcinoma (ILC) starts in the milk-producing glands (lobules) and can spread to other parts of the body. Invasive lobular carcinoma is the second most common form of invasive breast cancer, accounting for 10 - 15% of breast cancer cases.
Invasive breast cancers, like invasive ductal carcinoma or invasive lobular carcinoma, will most likely require an oncology team to create a treatment plan using one or more of the following:
Less Common Types of Breast Cancer
There are other types of breast cancer diagnoses that may be given based on what types of abnormal cells are found within the breast.
Inflammatory breast cancer
This is a less common type of breast cancer, accounting for 1-3% of all breast cancers. Inflammatory breast cancer typically appears at first as an infection with red, swollen and tender breasts rather than a tumor. This is because the cancer cells are blocking lymphatic vessels in the skin and breast tissue, causing a buildup of fluid (lymph), making the breast red, dimpled or painful to touch.
Paget’s disease of the nipple
This type of breast cancer starts in the breast ducts and spreads to the skin of the nipple and then to the areola, the dark circle around the nipple. Paget’s disease can be either intraductal or invasive.
Phyllodes tumors are rare breast tumors. These tumors develop in the connective tissue (stroma) of the breast and grow in a leaflike pattern. Although phyllodes tumors tend to grow quickly, they rarely spread outside the breast.
Angiosarcoma is cancer in the inner lining of blood vessels that can occur in any part of the body. This form of cancer rarely occurs in the breast.
This rare breast cancer is a subtype of invasive ductal carcinoma. It is named for it’s soft, fleshy resemblance to the brain’s medulla. It doesn’t normally grow quickly or spread into the lymph nodes.
Mucinous carcinoma, also known as colloid carcinoma, is a rare form of invasive ductal carcinoma where the tumor is made up of abnormal cells found in pools of mucin. Mucin is found in mucus, which lines our bodies digestive tracts, liver, lungs, and other organs. In mucinous carcinoma, however, mucin becomes part of the tumor and surrounds the breast cancer cells. Under a microscope, it looks like the cancer cells are scattered throughout pools of mucus.
Tubular carcinomas are usually small (about 1 cm or less) and made up of tube-shaped structures called "tubules." These tumors tend to be low-grade, meaning that their cells look somewhat similar to normal, healthy cells and tend to grow slowly. It is a subtype of invasive ductal carcinoma.
In invasive cribriform carcinoma, the cancer cells invade the connective tissues of the breast in nest-like formations between the ducts and lobules. Within the tumor, there are distinctive holes in between the cancer cells, making it look something like Swiss cheese. Invasive cribriform carcinoma is usually low grade, meaning that its cells look and behave somewhat like normal, healthy breast cells.
A very rare form of breast cancer, Invasive papillary carcinomas usually have a well-defined border and is made up of small, finger-like projections. If the cells are very small they are called micropapillary. In most cases, these types of tumors are diagnosed in older, postmenopausal women. In most cases of invasive papillary carcinoma, ductal carcinoma in situ is also present.