According to the National Cancer Institute, roughly 90% of women who get breast cancer live for at least five years or more. These improved statistics are attributed to advances in detection and treatment, and the fact that more women are having regular mammograms and other screening tests. There are several types of cancer that originate in breast tissue, and certain types are much more common than others.
The most common type of breast cancer begins in the milk ducts of the breast. The second most common type originates in the breast’s lobules, or glands that produce milk. These are both invasive—or infiltrating—cancers, meaning that they spread to other parts of the body if left untreated. Other types of breast cancer are less common.
Invasive Ductal Carcinoma
According to the Mayo Clinic, approximately 70 percent of women with breast cancer have invasive ductal carcinoma (IDC). The tumor, which feels like a lump, starts in the milk duct and then spreads to adjacent tissues. If not caught early enough, IDC can metastasize, or spread through the body, with cancerous cells carried via the bloodstream and the lymphatic system.
Invasive Lobular Carcinoma
Unlike IDC, invasive lobular carcinoma (ILC) makes the particular area of the breast feel enlarged. In other words, you will not feel a lump as you would with invasive ductal carcinoma. ILC accounts for 10 percent of cases among women with breast cancer, according to Genetic Health. Like IDC, invasive lobular carcinoma can metastasize to other areas of the body.
Upon diagnosis, invasive ductal and lobular carcinomas are assigned one of three grades by a pathologist. The purpose of grading is to determine how deformed the malignant (cancerous) breast tissue is, compared to normal, healthy tissue. Treatment options depend upon the grade. The tissue is given a grade of 1 if its underlying cells still look somewhat normal. A grade of 2 is assigned to tissue cells that start to look deformed. Grade 3 is assigned to the most advanced stages of IDC and ILC, in which the tissue cells have lost all normalcy, and are completely deformed.
Other less common types of breast cancers include medullary carcinoma, Paget’s disease and inflammatory breast cancer. Medullary carcinoma accounts for up to 6 percent of breast-cancer cases and is usually caused by genetic factors. Paget’s disease makes up 3 percent of all types of breast cancer, and is concentrated in the breast's areola and nipple. The inflammatory form accounts for up to 1 percent of breast-cancer cases, and is characterized by an inflammation of the breast caused by lymph-vessel blockage inside the skin.