Many women think of breast cancer as a single, invasive disease. In fact, there are various kinds of breast cancer. Some are more serious than others; some have distinctive signs and symptoms. Knowing a bit about the different kinds of breast cancer will help you in your quest to detect any problem early, when the chance of cure is best.
Breast cancer is classified according to where in the breast tissue it’s located and whether it’s spreading. Most breast cancers start in the milk ducts. These are tubes that carry milk from the lobules, where it’s produced, to the nipple. Cancers that occur in the milk ducts are called ductal cancers or ductal carcinomas (carcinoma is another term for cancer).
About 12 percent of breast cancers begin in the lobules and are called lobular cancers. The remaining breast cancers start in other breast tissue, such as lymph or blood vessels, fat or connective tissue.
After doctors determine a cancer’s location, its growth pattern is identified. A cancer that’s confined to the duct or lobule in which it started is referred to as a carcinoma in situ, meaning cancer “in place,” or as a noninvasive cancer.
Most noninvasive cancers, particularly the lobular type, never develop into invasive cancer. However, sometimes they’re a warning sign that invasive cancer may eventually develop somewhere in the breast. For example, ductal carcinoma in situ can sometimes turn into invasive breast cancer at a later date.
Noninvasive breast cancers rarely cause lumps that you can feel or any other symptoms, but they may appear as tiny areas of calcification (tiny flecks of calcium) on a mammogram.
Paget’s disease, a type of breast cancer that involves the nipple, accounts for about 3 percent of all breast cancers. Usually noninvasive, this cancer causes itching and flaking of the nipple that’s similar to the symptoms of eczema.
A breast cancer is classified as invasive or infiltrating if it has grown outside the duct or lobule where it started and into the surrounding tissue. This type of cancer may spread to the lymph nodes in the armpits and from there through the bloodstream to other parts of the body.
Seventy to 80 percent of all breast cancers are of the invasive ductal type. These cancers usually appear as a hard, firm lump, which may feel as though it’s “stuck” to the skin or chest wall. In advanced stages, the skin over the lump may appear dimpled or the nipple may be retracted (pulled inward).
Invasive lobular cancer begins in the lobules. Rather than appearing as a hard lump, this cancer may feel more like a thickening. Because it’s harder to detect—both on a mammogram and during physical examination—invasive lobular cancer is likely to be larger than ductal cancer when it’s first detected. Another difference: Invasive lobular cancer is slightly more likely to occur in both breasts than is invasive ductal cancer.
A few ductal or lobular cancers have a specific appearance when examined under a microscope. These cancers have been named according to their identifying characteristics. They include tubular carcinoma, which looks like little tubes; medullary carcinoma, which is the color of brain tissue (the medulla); mucinous carcinoma, which secretes mucous, and papillary carcinoma, which has little bumps (papules). These types account for only a small number of breast cancers. For all of them, the prognosis (likelihood that the patient will recover) is excellent.
There are other rare types of breast cancer. These include comedocarcinoma, inflammatory carcinoma, secretory carcinoma and adenocystic carcinoma.
Most breast cancers are detected as a painless lump, which is why annual clinical exams by a healthcare professional are so important in helping women to recognize the warning signs of cancer (see “What are the symptoms of breast cancer?”).
But breast exams are only part of the picture. By the time a cancer can be felt, it has been growing for some time. Mammograms are the most common way breast cancer can be detected in its early stages: Mammograms can detect a cancer up to two years before a lump can be felt. That’s important because, in the war against breast cancer, early detection means a better chance of a cure: Ninety-eight percent of women with localized breast cancer are still alive five years after diagnosis. Ultrasounds often are recommended as a follow-up if a mammogram shows cause for concern. Magnetic resonance imaging is a valuable tool for screening women at very high risk for breast cancer.