If you've been diagnosed with breast cancer, the first step your doctor may take will be to find the specifics of the tumor to determine your breast cancer type. This information can help guide your treatment.
Breast cancer can begin in different areas of the breast:
the milk ducts (ductal carcinoma),
the lobules (lobular carcinoma),
and in some cases in the connective tissue within the breast.
Nearly all breast cancers are either ductal carcinomas or lobular carcinomas.
Ductal carcinoma forms in the lining of a milk duct within your breast. The ducts carry breast milk from the lobules, where it's made, to the nipple.
Ductal Carcinoma In-Situ (DCIS)
DCIS is a type of early breast cancer that starts and remains confined to the layer of cells where it began inside of the ductal system. It is the most common type of non-invasive breast cancer. Non-invasive means that is has not spread beyond the ducts into the surrounding breast tissue. The cancer has remained in-situ which means "in its original place."
DCIS is not life-threatening but having DCIS can increase the risk of developing a new breast cancer or invasive breast cancer later on. Most recurrences of breast cancer happen within five to 10 years after initial diagnosis. The chances of a recurrence are under 30 percent.
About 1 in 5 new breast cancer cases will be DCIS. Nearly all women diagnosed at this early stage of breast cancer can be cured. A mammogram is often the best way to find DCIS early.
Infiltrating (Invasive) Ductal Carcinoma (IDC)
IDC is the most common type of breast cancer. An invasive cancer is one that has already grown beyond the layer of cells where it started (as opposed to carcinoma in situ). This is cancer that started in a milk duct, has broken through the wall of the milk duct, and has begun to invade the tissues of the breast. At this point, it may be able to spread (metastasize) to other parts of the body through the lymphatic system and bloodstream.
About 80 percent of all breast cancers are invasive ductal carcinomas. (Most breast cancers are invasive carcinomas -- either invasive ductal carcinoma or invasive lobular carcinoma.)
Less Common Ductal Carcinomas
There are some types of invasive ductal carcinoma that happen less commonly than others. In these cancers, the cells can look and behave somewhat differently than invasive ductal carcinoma cells usually do.
This is a rare subtype of invasive ductal breast carcinoma. Tubular carcinoma cells have a distinctive tubular structure when viewed under a microscope. In this type of cancer, the tumor is usually small and comprised of cells that are low grade. “Low grade” means they look somewhat similar to normal, healthy cells and tend to grow slowly.
Tubular carcinomas account for about 2% of all breast cancers. They are treated like invasive ductal carcinomas but tend to have a better prognosis than most breast cancers. Tubular carcinoma of the breast is less likely to spread outside the breast than other types of breast cancer and is easier to treat.
The average age of diagnosis for tubular carcinoma ranges from the mid-40s to late 60s.
This carcinoma of the breast is a rare subtype of invasive ductal carcinoma, accounting for about three to five percent of all cases of breast cancer. It most frequently occurs in women in their late 40s and 50s and is called “medullary” carcinoma because the tumor is a soft, fleshy mass that resembles the medulla (gray matter) of the brain.
Medullary carcinoma cells are usually high-grade in their appearance and low-grade in their behavior. In other words, they look like aggressive, highly abnormal cancer cells, but they don’t act like them.
Medullary carcinoma doesn’t grow quickly and usually doesn’t spread outside the breast to the lymph nodes. For this reason, it’s typically easier to treat than other types of breast cancer.
This cancer has a rather well-defined boundary between tumor tissue and normal tissue. It also has some other special features, including the large size of the cancer cells and the presence of immune system cells at the edges of the tumor.
Mucinous Carcinoma (Colloid)
This carcinoma of the breast, also known as colloid carcinoma, is a rare form of invasive ductal carcinoma. Mucinous carcinoma of the breast accounts for about 2-3% of all breast cancer cases.
In this type of cancer, the tumor is formed from abnormal cells that “float” in pools of mucin, a key ingredient in the slimy, slippery substance known as mucus.
Normally, mucus lines most of the inner surface of our bodies, such as our digestive tract, lungs, liver, and other vital organs. Many types of cancer cells, including most breast cancer cells, produce some mucus. In mucinous carcinoma, however, the mucus becomes a main part of the tumor and surrounds the breast cancer cells.
Mucinous carcinoma tends to affect women after they’ve gone through menopause. Some studies have found that the usual age at diagnosis is 60 or older.
Mucinous carcinoma is less likely to spread to the lymph nodes than other types of breast cancer making it easier to treat than more common types of invasive breast cancer.
Papillary Carcinoma of the Breast
Papillary carcinoma is often considered a subtype of ductal carcinoma in situ, and is treated as such. In rare cases, the tumor is invasive, in which case it is treated like invasive ductal carcinoma, although the outlook is likely to be better. These cancers tend to be diagnosed in older women who have already been through menopause, and they make up no more than 1% or 2% of all breast cancers.
An invasive papillary carcinoma usually has a well-defined border and is made up of small, finger-like projections.
On a scale of 1 to 3, with Grade 1 describing cancer cells that look and behave somewhat like normal, healthy breast cells, and Grade 3 describing very abnormal, fast-growing cancer cells, this cancer is often Grade 2, or moderate.
Lobular carcinoma starts in the lobules of the breast, where breast milk is produced. The lobules are connected to the ducts, which carry breast milk to the nipple.
Lobular Carcinoma In-Situ (LCIS)
LCIS is an area (or areas) of abnormal cell growth that increases a person’s risk of developing invasive breast cancer. Despite the fact that its name includes the term “carcinoma,” LCIS is not a true cancer, but is sometimes classified as a type of non-invasive breast cancer. It begins in the lobules (milk-producing glands at the end of the milk ducts) but it does not grow through the wall of the lobules.
Carcinoma refers to any cancer that begins in the skin or other tissues that cover internal organs — such as breast tissue. In situ or “in its original place” means that the abnormal growth remains inside the lobule and does not spread to surrounding tissues. People diagnosed with LCIS tend to have more than one lobule affected.
LCIS is an indication that a person is at higher-than-average risk for getting breast cancer at some point in the future. For this reason, some experts prefer the term “lobular neoplasia” instead of “lobular carcinoma.” A neoplasia is a collection of abnormal cells.
LCIS is usually diagnosed before menopause, most often between the ages of 40 and 50. Less than 10% of women diagnosed with LCIS have already gone through menopause. LCIS is extremely uncommon in men.
It is unknown exactly how many people are affected by LCIS because it does not cause symptoms and usually does not show up on a mammogram. It tends to be diagnosed as a result of a biopsy performed on the breast for some other reason.
Infiltrating (Invasive) Lobular Carcinoma (ILC)
This cancer is the second most common type of breast cancer after invasive ductal carcinoma (cancer that begins in the milk-carrying ducts and spreads beyond it).
Invasive means that the cancer has “invaded” or spread to the surrounding breast tissues. Lobular means that the cancer began in the milk-producing lobules, which empty out into the ducts that carry milk to the nipple. Carcinoma refers to any cancer that begins in the skin or other tissues that cover internal organs — such as breast tissue.
All together, “invasive lobular carcinoma” refers to cancer that has broken through the wall of the lobule and begun to invade the tissues of the breast. Over time, invasive lobular carcinoma can spread to the lymph nodes and possibly to other areas of the body. ILC usually appears as a subtle thickening in the upper-outer quadrant of the breast.
Although invasive lobular carcinoma can affect women at any age, it is more common as women grow older. ILC tends to occur later in life than invasive ductal carcinoma — the early 60s as opposed to the mid- to late 50s.
Some research has suggested that the use of hormone replacement therapy during and after menopause can increase the risk of ILC.
ILC can spread (metastasize) to other parts of the body. Invasive lobular carcinoma may be harder to detect by a mammogram than invasive ductal carcinoma.
Rare Breast Cancers
Connective Tissue Cancers
Rarely breast cancer can begin in the connective tissue that is made up of muscles, fat and blood vessels. Cancer that begins in the connective tissue is called sarcoma. Sarcomas are cancers that start from connective tissues such as muscle tissue, fat tissue, or blood vessels. Sarcomas of the breast are rare.
This rare cancer accounts for less than one percent of all breast tumors. The name "phyllodes," which is taken from the Greek language and means "leaf-like," refers to that fact that the tumor cells grow in a leaf-like pattern. Other names for these tumors are phyllodes tumor and cystosarcoma phyllodes. Phyllodes tumors tend to grow quickly, but they rarely spread outside the breast.
Although most phyllodes tumors are benign (not cancerous), some are malignant (cancerous) and some are borderline (in between noncancerous and cancerous). All three kinds of phyllodes tumors tend to grow quickly, and they require surgery to reduce the risk of a phyllodes tumor coming back in the breast (local recurrence).
Phyllodes tumors can occur at any age, but they tend to develop when a woman is in her 40s. Benign phyllodes tumors are usually diagnosed at a younger age than malignant phyllodes tumors. Phyllodes tumors are extremely rare in men.
Phyllodes tumors develop in the stroma (connective tissue) of the breast, in contrast to carcinomas, which develop in the ducts or lobules. These tumors are usually benign but on rare occasions may be malignant.
Benign phyllodes tumors are treated by removing the tumor along with a margin of normal breast tissue. A malignant phyllodes tumor is treated by removing it along with a wider margin of normal tissue, or by mastectomy. Surgery is often all that is needed, but these cancers may not respond as well to the other treatments used for more common breast cancers. When a malignant phyllodes tumor has spread, it may be treated with the chemotherapy given for soft-tissue sarcomas.
This is a form of cancer that starts from cells that line blood vessels or lymph vessels. It rarely occurs in the breasts. When it does, it usually develops as a complication of previous radiation treatments.
Angiosarcoma can also occur in the arm of women who develop lymphedema as a result of lymph node surgery or radiation therapy to treat breast cancer. These cancers tend to grow and spread quickly. Treatment is generally the same as for other sarcomas.
Cribriform Carcinoma of the Breast
In invasive cribriform carcinoma, the cancer cells invade the stroma (connective tissues of the breast) in nest-like formations between the ducts and lobules. Within the tumor, there are distinctive holes in between the cancer cells, making it look something like Swiss cheese.
Invasive cribriform carcinoma is usually low grade, meaning that its cells look and behave somewhat like normal, healthy breast cells. In about 5-6% of invasive breast cancers, some portion of the tumor can be considered cribriform. Usually, some ductal carcinoma in situ (DCIS) of the cribriform type is present as well.
Inflammatory Breast Cancer (IBC)
Inflammatory breast cancer is a rare and very aggressive type of breast cancer that causes the lymph vessels in the skin of the breast to become blocked. This type of breast cancer is called "inflammatory" because the breast often looks swollen and red, or "inflamed".
IBC usually starts with the reddening and swelling of the breast instead of a distinct lump or tumor. It also makes the breast feel warm and gives the breast skin a thick, pitted appearance that looks similar to an orange peel.
The affected breast may become larger or firmer, tender, or itchy. In its early stages, inflammatory breast cancer is frequently mistaken for an infection in the breast (called mastitis). Often this cancer is first treated as an infection with antibiotics. If the symptoms are caused by cancer, they will not improve, and the skin may be biopsied to look for cancer cells. Because there is no actual lump, it may not show up on a mammogram, which may make it even harder to find it early. This type of breast cancer tends to have a higher chance of spreading and a worse outlook than typical invasive ductal or lobular cancer.
IBC tends to grow and spread quickly, with symptoms worsening within days or even hours. It’s important to recognize symptoms and seek prompt treatment.
IBC accounts for 1% to 5% of all breast cancer cases in the United States.
Male Breast Cancer
While males do not have the same amount of hormones that stimulate breast tissue to grow into full breast as females do they occasionally can develop real breast gland tissue because they take certain medicines or have abnormal hormone levels and develop breast cancer.
Because breast cancer in men is rare (less than 1% of all breast cancers) few cases are available to study.
Paget's Disease of the Nipple
This is a rare form of breast cancer in which cancer cells collect in or around the nipple. The cancer usually affects the ducts of the nipple first (small milk-carrying tubes), then spreads to the nipple surface and the areola (the dark circle of skin around the nipple). The skin of the nipple and areola often appears crusted, scaly, and red, with areas of bleeding or oozing. The woman may notice burning or itching.
The unusual changes in the nipple and areola are often the first indication that breast cancer is present.
Paget's disease of the nipple accounts for less than 5% of all breast cancer cases in the United States. Being aware of the symptoms is important, given that more than 97% of people with Paget's disease also have ductal carcinoma in situ (DCIS) or, more often, infiltrating ductal carcinoma somewhere else in the breast.
Paget's disease of the nipple is more common in women, but like other forms of breast cancer, it can also affect men. The disease usually develops after age 50. According to the National Cancer Institute, the average age of diagnosis in women is 62, and in men, 69.
Treatment often requires mastectomy. If only DCIS is found (with no invasive cancer) when the breast is removed, the outlook is excellent.
Mixed tumors contain a variety of cell types, such as invasive ductal cancer combined with invasive lobular breast cancer. In this situation, the tumor is treated as if it were an invasive ductal cancer.
Triple-Negative Breast Cancer
This term is used to describe breast cancers (usually invasive ductal carcinomas) whose cells lack estrogen receptors and progesterone receptors, and do not have an excess of the HER2 protein on their surfaces.
Breast cancers with these characteristics tend to occur more often in younger women and in African-American women. Triple-negative breast cancers tend to grow and spread more quickly than most other types of breast cancer.
Because the tumor cells lack these certain receptors, neither hormone therapy nor drugs that target HER2 are effective against these cancers (but chemotherapy can still be useful if needed).
Metaplastic carcinoma is a very rare type of invasive ductal cancer. These tumors include cells that are normally not found in the breast, such as cells that look like skin cells (squamous cells) or cells that make bone. These tumors are treated like invasive ductal cancer.
Adenoid Cystic Carcinoma (adenocystic carcinoma)
These cancers have both glandular (adenoid) and cylinder-like (cystic) features when seen under the microscope. They make up less than 1% of breast cancers. They rarely spread to the lymph nodes or distant areas and they tend to have a very good prognosis.