Although breast cancer is often referred to as one disease, there are many different types of breast cancer.
All breast cancers start in the breast, so they are alike in some ways.
Breast cancers differ in other ways. They can be non-invasive or invasive. Tumor cells can vary in location (milk ducts or lobules) and how they look under a microscope. These differences often affect prognosis.
Tumor characteristics, such as hormone receptor status and HER2 status, also affect prognosis.
Learn more about factors that affect prognosis.
A pathologist looks at the tissue removed during a biopsy under a microscope to determine whether a tumor is non-invasive (ductal carcinoma in situ) or invasive breast cancer.
Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer. In situ means "in place." With DCIS, the abnormal cells are contained in the milk ducts of the breast and have not spread to nearby breast tissue.
Although DCIS is non-invasive, without treatment, the abnormal cells could progress to invasive breast cancer over time. So, you may also hear the terms “pre-invasive” or “pre-cancerous” to describe DCIS.
Learn more about breast anatomy.
Invasive breast cancer has spread from the original site (either the milk ducts or the lobules) into the nearby breast tissue, and possibly to the lymph nodes and other parts of the body.
For this reason, invasive breast cancers have a poorer prognosis than DCIS.
Figure 4.6 lists the types of invasive breast cancer.
Though they are not specific types of tumors, some special forms of breast cancer are discussed below.
Inflammatory breast cancer (IBC) is a rare, but aggressive form of locally advanced breast cancer.
It’s called inflammatory breast cancer because its main symptoms are swelling and redness (the breast often looks inflamed).
About 1-5 percent of breast cancers are IBC [21-22].
Learn more about IBC.
Paget disease of the breast (Paget disease of the nipple) is a rare cancer in the skin of the nipple or in the skin closely surrounding the nipple.
About 1-4 percent of breast cancers are Paget disease of the breast [23-24].
Learn more about Paget disease of the breast.
Metaplastic breast cancer is rare, accounting for fewer than 1 percent of all invasive breast cancers .
Compared to more common types of breast cancer, metaplastic tumors tend to:
They are also more likely to be triple negative [17,25-28]. Triple negative breast cancers are:
Under a microscope, metaplastic tumor cells can look very different from the tumor cells of more common breast cancers. So, these cancers can be hard to diagnose and are often confused with other uncommon breast tumors or tumors from other parts of the body.
It’s best to have the pathology slides sent out for review to confirm the diagnosis.
You can request your health care provider send the slides out for review or you may wish to get a second opinion for confirmation.
Learn more about getting a second opinion.
Most cancers that occur in the breast are breast cancers (breast carcinomas).
In rare cases:
Because these cancers are either not carcinomas or are carcinomas that don't start in the breast, they are treated differently and have different risk factors than breast cancer.
For more information on other cancers that can occur in the breast, such as lymphomas, sarcomas and malignant phyllodes tumors, visit the National Cancer Institute's website.
Facts for Life: Breast Cancer Prognosis
Breast Cancer 101 (Interactive Multimedia) - Tumors
Breast Cancer 101 - Tumor Size and Spread
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