Breast adenocarcinoma is the second most commonly diagnosed cancer in women, behind only skin cancer. Almost all breast cancers begin in the glands of the breast, including ducts and lobules. The term "adenocarcinoma" refers to the glandular nature of these breast cancers. There are three types of breast adenocarcinoma: ductal, lobular and sarcoma.
The first type of breast cancer is ductal carcinoma. This is the most common type of breast cancer, originating in the ducts that transport milk from the lobules to the nipples. There are two types of ductal cancer: in situ and invasive.
Ductal carcinoma in situ (DCIS) is the earliest form of breast adenocarcinoma and is considered a stage 0 cancer. DCIS cells are entirely confined to the duct itself, not having spread outside the walls. With early detection, the cure rate is almost 100 percent for this type of breast adenocarcinoma.
Invasive ductal carcinoma (IDC) accounts for nearly 80 percent of all breast cancers. IDC cells have spread from their location of origin, the ducts, into the fatty tissue of the breast. Invasive ductal carcinoma cells have the potential to metastasize, or spread throughout the body, via the bloodstream or lymphatic system. This type of cancer is described as stage I, II, III or IV, based on the size of the tumor and the extent to which it has spread.
The second type of breast cancer is lobular carcinoma. This type of breast adenocarcinoma originates in the milk-producing lobules of the breast. There are two types of lobular carcinoma: in situ and invasive.
Lobular carcinoma in situ (LCIS) is not considered an actual cancer; rather, LCIS is an area of abnormal tissue growth, sometimes called lobular neoplasia. LCIS cells are entirely confined within the walls of the lobules. Although LCIS cells are not cancerous themselves, their presence is a risk factor that indicates a higher potential for developing invasive lobular carcinoma. Studies have shown that women who have LCIS are 10-20 percent likely to develop invasive breast cancer during their lifetimes.
Invasive lobular carcinoma (ILC) represents lobular cancer cells that have spread from the lobules into the fatty tissues of the breast. Like IDC cells, these cancerous cells also have the potential to metastasize. Invasive lobular carcinoma accounts for 10-15 percent of all breast adenocarcinomas. This type of cancer is described as stage I, II, III or IV, based on the size of the tumor and the extent to which it has spread.
Sarcoma is a rare form of breast adenocarcinoma that originates in the connective tissues of the breast. These tissues include muscle, fat and blood vessels. Examples of sarcomas include phyllode tumors and angiocarcinoma.
Invasive breast adenocarcinoma generally is graded on a scale of 1-3. These grades are based on the observed difference between the cancerous cells and the surrounding healthy cells. Grade 3 breast cancer cells represent the largest difference and are considered the most aggressive.
Some types of breast cancers are influenced by naturally occurring female hormones, such as estrogen and progesterone. Breast cancers that utilize estrogen to grow are called estrogen receptor (ER) positive. Those that utilize progesterone to grow are called progesterone receptor (PR) positive. In these cases, hormone blocking medications can be used to slow the growth of the breast adenocarcinomas.