Types of Tumors
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.
Non-invasive and invasive breast cancers
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)
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
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.
Types of invasive breast cancer
Figure 4.6 lists the types of invasive breast cancer.
- Invasive ductal carcinoma is the most common type of breast cancer (70-80 percent of all breast cancers) [17,20]. It may also be called infiltrating ductal carcinoma, invasive carcinoma of no special type or invasive carcinoma not otherwise specified.
- Invasive lobular carcinoma is the next most common type (10-15 percent of breast cancers) [17,20].
|Types of invasive breast cancer||Proportion of all invasive breast cancers||Tumor characteristics||Prognosis|
|Invasive ductal carcinoma (IDC)||70-80%|
|Invasive lobular carcinoma (ILC)||10-15%|
|Mucinous (colloid) carcinoma||2%|
|Carcinomas with medullary features||Less than 1%|
|Invasive papillary carcinoma||Less than 1%|
|* Percentage is higher in cancers found through mammography screening.|
ER-positive = estrogen receptor-positive
ER-negative = estrogen receptor-negative
PR-negative = progesterone receptor-negative
HER2-negative = HER2 receptor-negative
|Adapted from select sources [17,20].|
Special forms of breast cancer
Though they are not specific types of tumors, some special forms of breast cancer are discussed below.
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Other types of cancer that occur in the breast
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.
- Cancers from other sites can metastasize (spread) to the breast and mimic breast cancers.
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.
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