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, but differ in others. They can be non-invasive or invasive. Tumor cells can vary in location (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 develop into 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/or 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 (so the breast often looks inflamed).
About 1-5 percent of breast cancers are IBC [14-15].
Learn more about IBC.
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 [13,17-20].
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 that 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, other types of cancer such as lymphomas (cancer of the lymph system) and sarcomas (cancer of the soft tissues) can occur in the breast.
Rarely, cancers from other sites can metastasize (spread) to the breast and mimic breast cancers.
Because these cancers are not carcinomas, they are treated differently and have different risk profiles than breast cancer.
For more information on other cancers that can occur in the breast, such as lymphomas and malignant phyllodes tumors, visit the National Cancer Institute's website.
Facts for Life: Types of Breast Cancer Tumors
Facts for Life: Breast Cancer Prognosis
Breast Cancer 101 (Interactive Multimedia) - Tumors
Breast Cancer 101 - Tumor Size and Spread
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