What types of breast cancer are there?
Breast cancer is a type of uncontrolled growth of abnormal cells that can develop in one of several different areas of the breast, including the ducts that carry milk to the nipple, the breast's lobules (small sacs that produce milk) and the breast's
Breast cancer was originally described according to its appearances, so words like scirrhous (meaning woody) were used and still appear in the literature. More recently, breast cancer has been classified according to its appearances when under the microscope. Early pathologists classified breast cancers into 'invasive ductal' cancers and 'invasive lobular' cancers believing that invasive ductal cancers arose in ducts and invasive lobular cancers in the lobules. However, it is now clear that all invasive ductal and invasive lobular cancers arise either in the terminal duct or the lobule. As the terms invasive ductal and lobular are in such common usage and as they have different appearances under the microscope they are still used.
A more logical classification divides tumours into those of 'special' and 'no special' type. Invasive carcinoma of no special type is also commonly referred to as invasive ductal carcinoma. It is the most common type and accounts for up to 85 per cent of all breast cancers. Special types of tumour have particular microscopic features and these include invasive lobular carcinoma, invasive tubular, cribriform, medullary and mucinous cancers, with other types being uncommon. Many of the special type cancers have a better prognosis - in other words the patient has a higher chance of survival.
When a cancer is examined under the microscope, it is usually possible to assess how aggressive it is: in other words how far and how fast it is likely to spread. The tumour may be assigned to one of three grades ranging from grade I to grade III in order of seriousness. For instance, a grade I cancer is non-aggressive and unlikely to cause harm. In contrast, grade III tumours are aggressive and likely to cause harm, but can sometimes be controlled with effective treatment.
The main forms of breast cancer are:
Invasive ductal carcinoma -This type of breast cancer develops in the milk ducts and accounts for about 79 percent of cases. It can break through the duct wall and invade the breast's fatty tissue, then metastasize (spread) to other parts of the body through the bloodstream or lymphatic system.
Invasive lobular carcinoma - This type of breast cancer accounts for about 10 percent of cases and originates in the breast's milk-producing lobules. It also can spread to the breast's fatty tissue and other places in the body.
Medullary, mucinous and tubular carcinomas - These are three slow-growing types of breast cancer. Together they represent about 10 percent of all breast cancers.
Paget's disease - This type represents about 1 percent of breast cancers. It starts in the milk ducts of the nipple and can spread to the areola (dark circle around the nipple). Women who get Paget's disease usually have a history of nipple crusting, scaling, itching or inflammation.
Inflammatory carcinoma This type accounts for about 1 percent of all cases. Of all breast cancers, inflammatory carcinoma is the most aggressive and difficult to treat, because it spreads so quickly.
As more women have regular mammograms, doctors are also detecting many more noninvasive or precancerous conditions before they become full-blown cancer. These conditions include:
Ductal carcinoma in situ (DCIS) - DCIS occurs when cancer cells fill the ducts but haven't yet spread through the walls into fatty tissue. Nearly all women diagnosed at this early stage can be cured. Without treatment, about 25 percent of DCIS cases will lead to invasive breast cancer within 10 years.
Lobular carcinoma in situ (LCIS) - LCIS is less common and less of a threat than DCIS. It develops in the breast's milk-producing lobules. LCIS doesn't require treatment, but it does increase a woman's risk of developing breast cancer.