Types of Breast Cancer

Memorial Sloan Kettering medical oncologist Andrew Seidman discusses treatment options with a breast cancer patient

What are the types of breast cancer, and what do they mean? Breast cancer types are determined by the way a sample of cells from the tumor, collected during a breast biopsy or breast cancer surgery, looks under a microscope. Breast cancers are also classified according to how sensitive they are to the hormones estrogen and progesterone, their levels of certain proteins that play a role in breast cancer growth (such as HER2), their genetic makeup, and other characteristics. This classification helps doctors predict how a cancer will respond to specific treatments, and it also allows them to personalize treatment.

Use this guide to learn about a variety of types of breast cancer and how they are classified.

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What is invasive breast cancer versus noninvasive breast cancer?

Noninvasive cancer means the abnormal cells are contained in the milk ducts of the breast and lack the ability to spread to surrounding tissue or elsewhere in the body. Invasive breast cancer means the cancer has grown beyond its original location into surrounding normal breast tissue and has the potential to spread to other parts of the body.

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What is ductal carcinoma in situ?

Ductal carcinoma in situ (DCIS) is a very early form of breast cancer that’s confined to the milk ducts, which is why it’s called “ductal.” “Carcinoma” is the name for any cancer that begins in cells that line the inner or outer surfaces of tissues, such as the breast ducts. “In situ” is a Latin term meaning “in its original place.” DCIS is the most common form of noninvasive breast cancer.

DCIS is classified as low, intermediate, or high grade. Grades are based on what the cells look like under a microscope. The lower the grade, the more closely DCIS resembles normal breast cells. The higher the grade, the more different it is from normal cells. DCIS can sometimes involve the nipple, causing it to look red and scaly. This is a rare form of cancer known as Paget’s disease of the breast (named after the doctor who first described it).

In some women, DCIS may not progress to invasive cancer in their lifetime. This has fueled debate about whether women with low-risk DCIS (those with low- or intermediate-grade disease and no family history of breast cancer) need any treatment, or if they could be safely checked with annual mammograms and breast exams to see if the cancer is progressing. Currently, the standard treatment for DCIS includes surgery, often a lumpectomy.

When Memorial Sloan Kettering doctors studied 1,850 women with DCIS, we found that only about 16% (296) had low-risk DCIS. Of those, about 20% of them already had invasive cancer. Based on this study and other research, we believe that for most DCIS patients, surgical removal and lab analysis of the affected area is the only way to tell for sure whether a woman with DCIS also has invasive cancer. A major goal of future research is to discover ways to identify women with DCIS that won’t progress to invasive cancer, so they can avoid unnecessary treatment.

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What is invasive ductal carcinoma?

Invasive ductal carcinoma is a type of cancer that starts in the milk ducts and spreads to surrounding tissue. This is the most common form of breast cancer. Of the 245,000 American women diagnosed with invasive breast cancer each year, about 75% of them have invasive ductal carcinoma.  

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What is invasive lobular carcinoma?

Invasive lobular carcinoma (ILC) is a cancer that starts in the breast’s lobules and invades surrounding tissue. ILC is the second most common form of invasive breast cancer, accounting for 10 to 15% of breast cancer cases. ILC doesn’t always form a lump, but women who have it may notice a thick or full area that doesn’t feel like the rest of the breast.

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What are lobular carcinoma in situ and atypical lobular hyperplasia?

Lobular carcinoma in situ (LCIS) is not considered breast cancer or a precancer because it doesn’t turn into invasive cancer if untreated. LCIS and atypical lobular hyperplasia (ALH), a similar noncancerous condition, are subtypes of lobular neoplasia, a disorder marked by abnormal cells in the breast’s lobules (milk-producing glands). Since LCIS and ALH raise your risk for breast cancer in the future, if you’ve been diagnosed with either of them, talk to your doctor about how often you should be screened for breast cancer and whether you should have any additional screening tests.

Learn more about hyperplasia.

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What is inflammatory breast cancer?

As its name suggests, inflammatory breast cancer (IBC) often causes the breast to become red, swollen, and inflamed. Some women with IBC also notice thickened or discolored breast skin with tiny dimples, puckers, or ridges that make it look like an orange peel. While the symptoms may sound like an infection, the real culprit is cancer that is blocking lymphatic vessels in the skin and breast tissue, causing a buildup of fluid (lymph) and, in some cases, pain, discoloration, and sudden swelling of the breast. Also called inflammatory breast carcinoma or locally advanced breast cancer, IBC can spread quickly, making prompt diagnosis and treatment essential.

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What is breast sarcoma?

Breast sarcoma is a very rare form of breast cancer. Instead of cancer forming in the lobes or ducts, a tumor may form in the connective or fibrous tissue surrounding them. Sarcomas account for only 1% of all breast cancers.

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What is metaplastic carcinoma?

Also known as metaplastic breast cancer, metaplastic carcinoma is a rare type of invasive breast cancer with a unique characteristic: It contains a mix of two or more types of breast cancer cells, usually carcinoma combined with sarcoma. “Metaplastic” means that one form is turning into another. Various leading-edge techniques are used to analyze the exact genetics and biology of these confused cancers to find out if the tumor is more similar to carcinoma or sarcoma, since these two types of cancer have very different treatments.

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What is estrogen receptor–positive breast cancer and progesterone receptor–positive breast cancer?

Cells from your breast cancer can be tested for receptors on two hormones that can fuel cancer growth: estrogen and progesterone. Receptors are special proteins on cells that attach to certain substances, such as estrogen and progesterone, much like a key entering a lock. Breast cancer can contain receptors for one of these hormones, both, or neither.

  • Breast cancer with receptors for estrogen is called estrogen receptor positive, or ER positive.
  • Breast cancer with no receptors for estrogen is called estrogen receptor negative, or ER negative.
  • Breast cancer with receptors for progesterone is called progesterone receptor positive, or PR positive.
  • Breast cancer with no receptors for progesterone is called progesterone receptor negative, or PR negative.

If your cancer is ER positive, PR positive, or positive for both estrogen and progesterone receptors, your treatment may include a targeted therapy — a drug or drugs that keep these hormones from plugging into their receptors. The idea is to cut off the cancer’s access to the fuel that would otherwise power its growth, much like putting a child safety cap on an electrical outlet. 

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What is HER2-positive breast cancer?

HER2/neu is a gene in cells that acts like an on/off switch to produce a protein called HER2. This protein normally helps control how healthy breast cells grow and divide. However, about one in five breast cancers either has extra copies of the HER2/neu gene or produces an oversupply of this protein. This type of cancer is called HER2 positive and makes cells grow in an uncontrolled way. If your cancer is HER2 positive, it can be treated with drugs that block HER2 receptors.

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What is triple-negative breast cancer?

About 10 to 15% of breast cancers are classified as triple negative because they lack receptors for estrogen, progesterone, and HER2. They can be harder to treat because they don’t respond to drugs that target estrogen, progesterone, or HER2 receptors. Women with triple-negative breast cancer are mainly treated with chemotherapy or take part in clinical trials.

Studies show that genetic mutations are more common in women with triple-negative breast cancer, even if they don’t have any family history of breast cancer. If you have triple-negative breast cancer, talk to your doctor about genetic counseling and testing for hereditary forms of breast cancer, such as those linked to the BRCA1 and BRCA2 genes and other genetic mutations. Knowing if you have a genetic mutation helps your doctors determine the best treatment plan and may have implications for cancer risk for your relatives.

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What is a breast papilloma, and is it cancer?

Also called intraductal papilloma, a breast papilloma is a small, wartlike growth in the breast’s milk ducts. This benign (noncancerous) condition may cause a clear or bloody discharge from the nipple, or you may feel a small lump behind or next to the nipple. Having one papilloma does not raise your breast cancer risk, though having several of these growths has been linked to higher risk. 

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