According to the Centers for Disease Control and Prevention, breast cancer is the most common cancer in women in the United States and the second most common cause of death from cancer after lung cancer. Though much less common than in women, it does occur in men, with cases in men accounting for less than one percent of cases.
Histology of breast cancer is determined by subjecting a sample taken from the breast, by biopsy, to further specialized laboratory examination. According to the Mayo Clinic, certain characteristics determine the type of breast cancer.
Ductal Carcinoma
This is the most common type of breast cancer, arising from the milk ducts in the breast, the pipes that carry milk from the lobules, where it is produced, to the nipple, where it is discharged.
Ductal carcinoma can be confined to the ducts without spreading outside the ducts to nearby structures. This is called non-invasive ductal carcinoma or ductal carcinoma in-situ. It is the most common type of non-invasive cancer in women, accounting for 80 percent of non-invasive cancer, according to the WHO.
Invasive ductal carcinoma, the most common form of breast cancer, according to the American Cancer Society, is the diagnosis when the cancer has spread beyond the walls of the ducts into surrounding structures and even spreading beyond the breast to become metastatic ductal carcinoma.
Some less common sub-types of invasive ductal carcinoma are tubular carcinoma of the breast, mucinous carcinoma of the breast, papillary carcinoma of the breast, medullary carcinoma of the breast, cribriform carcinoma of the breast, metaplastic carcinoma of the breast and mixed carcinoma of the breast.
Paget's disease of the nipple is another type of invasive cancer, which, according to the American cancer society, is almost always associated with ductal carcinoma.
Lobular Carcinoma
This is cancer arising from the milk producing areas of the breast. When it is localized to the lobules of the breast, without any evidence of spread, it is called lobular carcinoma in-situ. Spread beyond the lobules classifies it as invasive lobular carcinoma.
Inflammatory Breast Cancer
This is a form of invasive breast cancer that usually first appears as an infection or inflammation of the breast, with the breast feeling warm and tender and looking like an orange skin in appearance. According to the American Cancer Society, this type of cancer is extremely difficult to pick up on mammography, since there are no actual localized masses or lumps. It is also more likely to spread and has a poorer outlook than the ductal or lobular types of cancer.
Adenoid Cystic Carcinoma
This type of breast cancer, also called adenocystic carcinoma, is associated with a combined picture of glandular and tubular features. It is considered to have a better outlook than other breast cancers.
Triple Negative Breast Cancers
These are breast cancers that do not behave like the usual breast cancers with receptors for the female sex hormones, estrogen and progesterone, on their cell surfaces. According to the American Cancer Society, they are much more aggressive and have the poorest outlook of all breast cancers.
Other Types of Breast Cancer
Other types of breast cancer that are not so common include cystisarcoma phylloides, arising from the connective tissue of the breast, and angiosarcomas, arising from the cells in the walls of blood or lymphatic vessels in the breast. Angiosarcomas, according to the American Cancer Society, usually arise due to previous exposure to radiation, particularly following cancer treatment.
