Breast Cancer Types
A breast cancer’s type is determined by the specific cells in the breast that become cancer.
Ductal or lobular carcinoma
Most breast cancers are carcinomas, which are tumors that start in the epithelial cells that line organs and tissues throughout the body. When carcinomas form in the breast, they are usually a more specific type called adenocarcinoma, which starts in cells in the ducts (the milk ducts) or the lobules (glands in the breast that make milk).
In situ vs. invasive breast cancers
The type of breast cancer can also refer to whether the cancer has spread or not. In situ breast cancer (ductal carcinoma in situ or DCIS) is a pre-cancer that starts in a milk duct and has not grown into the rest of the breast tissue. The term invasive (or infiltrating) breast cancer is used to describe any type of breast cancer that has spread (invaded) into the surrounding breast tissue.
Breast Cancer Hormone Receptor Status
Breast cancer cells taken out during a biopsy or surgery will be tested to see if they have certain proteins that are estrogen or progesterone receptors.
When the hormones estrogen and progesterone attach to these receptors, they stimulate the cancer to grow. Cancers are called hormone receptor-positive or hormone receptor-negative based on whether or not they have these receptors (proteins).
Breast cancer cells may have one, both, or none of these receptors but about two out of every three breast cancers will have at least one type of hormone receptor.
Knowing the hormone receptor status is important in deciding treatment options. Hormone status is defined as follows:
- ER positive (ER+): the breast cancer cells have estrogen receptors
ER negative (ER-): the breast cancer cells do not have estrogen receptors - PR positive (PR+): the breast cancer cells have progesterone receptors
PR negative (PR-): the breast cancer cells do not have progesterone receptors - HER2 positive (HER2+) (Human epidermal growth factor type 2 receptor – also known as ERBB2): the breast cancer cells have larger than normal amounts of HER2 receptors on their surface.
HER2+ breast cancer is more likely to grow and divide faster than HER2- breast cancer.
Outlook for HER2-Positive Breast Cancer
7-year disease-free: Around 93%
10-year disease-free: About 70%-75%
HER2 negative (HER2-): the breast cancer cells have a normal amount of HER2 on their surface. - HER2-low breast cancer A large number of breast cancers considered HER2-negative have some HER2 proteins on the surface of their cells. There just aren’t enough HER2 proteins for the cancer to be considered HER2-positive. Doctors now call these cancers HER2-low.
- Triple positive: the breast cancer cells have estrogen receptors, progesterone receptors, and a larger than normal amount of HER2 receptors.
Triple negative: the breast cancer cells do not have estrogen receptors, progesterone receptors, or a larger than normal amount of HER2 receptors.
Ductal Carcinoma In Situ (DCIS)
About 1 in 5 new breast cancers will be ductal carcinoma in situ (DCIS). DCIS is also called intraductal carcinoma or stage 0 breast cancer.
DCIS is a non-invasive or pre-invasive breast cancer. This means the cells that line the ducts have changed to cancer cells but they have not spread through the walls of the ducts into the nearby breast tissue.
Nearly all women with this early stage of breast cancer can be cured.
Invasive Breast Cancer
Breast cancers that have spread into surrounding breast tissue are known as invasive breast cancers.
Most breast cancers are invasive, but there are different types of invasive breast cancer. The two most common are invasive ductal carcinoma and invasive lobular carcinoma.
Inflammatory breast cancer is also a type of invasive breast cancer.
Invasive ductal carcinoma
This is the most common type of breast cancer. About 8 in 10 invasive breast cancers are invasive (or infiltrating) ductal carcinomas (IDC).
IDC is an invasive cancer where abnormal cancer cells that began forming in the milk ducts have spread beyond the ducts into other parts of the breast tissue. At this point, it may be able to spread (metastasize) to other parts of the body through the lymph system and bloodstream.
- IDC is the most common type of breast cancer, making up nearly 70- 80% of all breast cancer diagnoses.
IDC is also the type of breast cancer that most commonly affects men.
Invasive lobular carcinoma (ILC)
About 1 in 10 invasive breast cancers is an invasive lobular carcinoma (ILC).
ILC starts in the breast glands that make milk (lobules). Like IDC, it can spread (metastasize) to other parts of the body. Invasive lobular carcinoma may be harder to detect on physical exam and imaging, like mammograms, than invasive ductal carcinoma. And compared to other kinds of invasive carcinoma, it is more likely to affect both breasts. About 1 in 5 women with ILC might have cancer in both breasts at the time they are diagnosed.
Roughly one-in-five invasive breast cancers are categorized as triple negative, meaning they do not rely on the hormones estrogen and progesterone for growth, nor on human epidermal growth factor receptor 2 (HER2). Given this, they are not vulnerable to modern hormonal therapies or to the HER2-targeted drug Herceptin (trastuzumab). Because they grow rapidly in early stages, triple-negative breast tumors often respond well initially to older chemotherapies that kill dividing cells, but a greater percentage of women diagnosed with this type of breast cancer die within five years of diagnosis because of the emergence of cancer metastasis.
Lobular Carcinoma In Situ?
Lobular Carcinoma In Situ (LCIS) is not breast cancer. It is a condition where abnormal cells are found in the lobules of the breast. The atypical cells have not spread outside of the lobules into the surrounding breast tissue.
LCIS is highly treatable and seldom becomes invasive cancer. However, having LCIS in one breast increases the risk of developing breast cancer in either breast.
What Does The Term “In Situ” Mean?
Although LCIS is not considered breast cancer, it still has the term carcinoma in the name. The earliest stages of cancers are called “carcinoma in situ.” Carcinoma means “cancer” and in situ means “in the original place.”
Inflammatory Breast Cancer
Inflammatory breast cancer (IBC) is rare and accounts for only 1% to 5% of all breast cancers. Although it is a type of invasive ductal carcinoma, its symptoms, outlook, and treatment are different. IBC causes symptoms of breast inflammation like swelling and redness, which is caused by cancer cells blocking lymph vessels in the skin causing the breast to look “inflamed.”
Inflammatory breast cancer (IBC) differs from other types of breast cancer in many ways:
- IBC doesn’t look like a typical breast cancer. It often does not cause a breast lump, and it might not show up on a mammogram. This makes it harder to diagnose.
- IBC tends to occur in younger women (younger than 40 years of age).
- Black women appear to develop IBC more often than White women.
- IBC is more common among women who are overweight or obese.
- IBC tends to be more aggressive—it grows and spreads much more quickly—than more common types of breast cancer.
- IBC is always at least at a locally advanced stage when it’s first diagnosed because the breast cancer cells have grown into the skin. (This means it is at least stage III.)
- In about 1 of 3 cases, IBC has already spread (metastasized) to distant parts of the body when it is diagnosed. This makes it harder to treat successfully.
- Women with IBC tend to have a worse prognosis (outcome) than women with other common types of breast cancer.
What Is Metastatic Breast Cancer?
Metastatic breast cancer is also classified as Stage 4 breast cancer. The cancer has spread to other parts of the body. This usually includes the lungs, liver, bones or brain.
Less common cancer types
Though the most common breast cancer type is invasive ductal carcinoma (IDC), there are other types that are less commonly seen.
- Medullary Carcinoma
Medullary carcinoma accounts for 3-5% of all breast cancer types. The tumor usually shows up on a mammogram, but does not always feel like a lump.
- Tubular Carcinoma
Making up about 2% of all breast cancer diagnosis. It is usually found through a mammogram. This type of breast cancer is known for being slow growing and is usually associated with DCIS. Typically this type of breast cancer is found in women aged 50 and above and usually responds well to hormone therapy.
- Mucinous Carcinoma (Colloid)
Represents approximately 1% to 2% of all breast cancers. It has a favorable prognosis in most cases.
- Paget’s Disease Of The Breast Or Nipple
This is a rare type of cancer affecting the skin of the nipple and often the areola. Most people with Paget’s disease evident on the nipple also have one or more tumors inside the same breast; generally either ductal carcinoma in situ or invasive breast cancer.
- Metaplastic Breast Cancer
A very rare and aggressive form of breast cancer. It accounts for less than 1% of all breast cancer diagnoses.
- Phyllodes Tumors
Phyllodes tumors in the breast are usually benign (non-cancerous), with only a small percentage found to be malignant (cancerous). Though rare, the presence of malignant phyllodes tumors in the breast often requires a mastectomy as part of treatment.
- Angiosarcoma of the Breast
Angiosarcoma of the breast is an extremely rare form of breast cancer, accounting for only 0.1% to 0.2% of all breast cancers. It occurs in the breast and in the skin of the arms, and is usually seen in those who have had extensive prior radiation of the chest wall, such as mantle radiation for cancer treatment as a child or young person. Angiosarcoma can grow and spread quickly.
- Adenoid cystic carcinoma
An uncommon type of cancer that usually develops in the salivary glands or other areas of the head and neck. Sometimes it can form in other parts of the body, including your skin, breast tissue, cervix or prostate gland. - Low-grade adenosquamous carcinoma
A rare variant of metaplastic breast carcinoma, incidentally detected during screening. - Papillary carcinoma
Papillary carcinoma is estimated to be only 1% to 2% of breast carcinoma in women. - Metaplastic carcinoma
Metaplastic breast cancer (MBC) is a rare neoplasm that accounts for less than 1% of all breast cancers. - Micropapillary carcinoma
Metaplastic breast cancer is a rare, aggressive form of breast cancer. It is usually discovered as a fast-growing lump or mass in the breast. - Mixed carcinoma
Has features of both invasive ductal and invasive lobular cancers.
Types of non-cancerous breast conditions
Fibrosis and Simple Cysts
Hyperplasia (Ductal or Lobular)
Lobular Carcinoma in Situ (LCIS)
Adenosis
Fibroadenomas
Phyllodes Tumors
Intraductal Papillomas
Fat Necrosis and Oil Cysts
Mastitis
Duct Ectasia
Radial Scars and Other Non-cancerous Breast Conditions
Resources
National Breast Cancer Foundation
American Cancer Society
Penn medicine
University of California San Francisco
National Cancer Institute
Mayo Clinic
Cleveland Clinic
Healthline
WebMD
Breastcancer.org
MD Anderson Cancer Center