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 into the surrounding breast tissue. (For more on breast structure, see Figure 1.1).
Although DCIS is non-invasive, without treatment, the abnormal cells could turn into invasive breast cancer over time. So, you may also hear the term pre-invasive breast cancer to describe DCIS. Learn more about DCIS.
Invasive breast cancer has spread from the original site (either the milk ducts or the lobules) into the surrounding breast tissue, and possibly spread to the lymph nodes and/or other parts of the body. For this reason, invasive breast cancers have a poorer prognosis than DCIS.
Using a microscope to look at the tissue removed during a biopsy, a pathologist can determine whether a tumor is DCIS or invasive breast cancer.
Figure 4.6 below lists the types of invasive breast cancer. The most common type is invasive ductal carcinoma (also called infiltrating ductal carcinoma and less commonly, invasive carcinoma of no special type or invasive carcinoma not otherwise specified). Invasive ductal carcinoma accounts for 50 to 75 percent of all breast cancers .
Invasive lobular carcinoma is the next most common type and accounts for about 10 to 15 percent of cases .
Tubular carcinoma and mucinous (colloid) carcinoma are less common types of invasive breast cancer that tend to have a good prognosis [8,17].
Figure 4.6: Prevalence and Tumor Characteristics of Different Types of Invasive Breast Cancer
Types of invasive breast cancer
Proportion of all invasive breast cancers
Invasive ductal carcinoma (IDC)
Invasive lobular carcinoma (ILC)
Mucinous (colloid) carcinoma
Less than 1%
* Percentage is higher in cancers found through mammography screening.
ER+ = estrogen receptor-positive ER- = estrogen receptor-negative PR- = progesterone receptor-negativeHER2- = HER2/neu receptor-negative
Adapted from selected sources [17-19].
Tumor size is highly related to prognosis. In most cases, the smaller the tumor, the better the chances are for long-term survival.
A health care provider can estimate the size of the tumor by feeling it during a physical exam. Images from an ultrasound or mammogram can also be used to estimate tumor size. However, the most accurate way to assess size is to measure the entire tumor after it has been removed from the breast. The pathologist will take these measurements during his/her exam and record them in your pathology report.
Learn more about a pathology report.
Tumor grade is a way of classifying tumors based on certain features of their cells. The grade of a tumor is directly linked to prognosis.
Using a microscope, a pathologist studies the tumor tissue removed during a biopsy to check:
Together, these two factors determine the tumor grade. These grades are usually classified as:
For any given tumor size and breast cancer stage, prognosis is poorer with a higher tumor grade. Many other factors also impact survival and for any given tumor grade, survival varies greatly depending on these factors.
Hormone receptor status is a main factor in planning breast cancer treatment. Some breast cancer cells grow with the help of estrogen and/or progesterone (female hormones produced in the body). These cancer cells have special proteins inside, called hormone receptors. When hormones attach to hormone receptors, the cancer cells with these receptors grow.
A pathologist determines the hormone receptor status by testing the tumor tissue removed during a biopsy.
Most (about two out of three) breast cancers are hormone receptor-positive .
Hormone receptor-positive breast cancers can be treated with hormone therapies. These include tamoxifen and the aromatase inhibitors, anastrozole (Arimidex), letrozole (Femara) or exemestane (Aromasin).
Hormone receptor-negative breast cancers are not treated with hormone therapies because they do not have hormone receptors.
Breast cancers that are ER+ also tend to be PR+. And, cancers that are ER- tend to be PR-.
Sometimes, a breast cancer is positive for estrogen receptors, but negative for progesterone receptors. Because current hormone therapies are designed to treat ER+ cancers, these cases are treated the same as breast cancers that are positive for both hormone receptors.
Hormone therapies can stop tumor growth (in hormone receptor-positive cancers) by preventing the cancer cells from getting the estrogen they need to grow. They can do this in different ways. Some hormone therapies, like the drug tamoxifen, attach to hormone receptors inside the cancer cells and block estrogen from attaching to the receptors. Other therapies, like aromatase inhibitors, lower the level of estrogen in the body so the cancer cells cannot get the estrogen they need.
Hormone receptor status is also related to the chance of recurrence (the return of breast cancer after treatment). Hormone receptor-positive tumors have a slightly lower chance of breast cancer recurrence than hormone receptor-negative tumors in the first five years after diagnosis. However, after five years, this difference begins to decrease and over time, goes away [6,29].
Learn more about hormone therapies.
Learn about hormone receptor status information on a pathology report.
For a summary of research studies on hormone receptor status,
visit the Breast Cancer Research section.
HER2/neu (human epidermal growth factor receptor 2), also called ErbB2, is a protein that appears on the surface of some breast cancer cells. This protein is an important part of the pathway for cell growth and survival.
About 15 to 20 percent of all breast cancers are HER2+ (you also may hear the term “HER2/neu over-expression”) [30-31]. HER2/neu status helps guide treatment.
Read Research Fast Facts: HER2-Positive Breast Cancer (PDF)
HER2+ breast cancers can benefit from anti-HER2/neu drugs, such as the drug trastuzumab (Herceptin), which directly target the HER2/neu receptor . Trastuzumab and other anti-HER2/neu targeted therapies are not used for HER2- cancers.
Learn about trastuzumab in the treatment of early and locally advanced breast cancer.
Learn about trastuzumab, lapatinib and other targeted therapies in the treatment of metastatic breast cancer.
Learn about emerging targeted therapies for HER2/neu-positive metastatic breast cancer.
All tumors should be tested for HER2/neu status. The two common ways to determine HER2/neu status are:
Learn about HER2/neu status information on a pathology report.
How fast a tumor grows (known as its proliferation rate) can help show how aggressive a tumor is and how likely it is to spread to other parts of the body. Tumors with a high proliferation rate (those that are growing fast) often have a poorer prognosis than those with a low proliferation rate.
Proliferation rate is an important predictor of prognosis and whether or not a tumor will respond to chemotherapy. However, there are issues related to its measurement. So, while some health care providers may use it to help guide treatment options, others do not.
The Ki-67 test is a common way to measure proliferation rate. When cells are growing and dividing (proliferating), they make proteins called proliferation antigens. By counting the number of cells with these antigens, a pathologist can determine a tumor's proliferation rate.
The antibody to Ki-67 attaches itself to the proliferation antigen. The more cells the Ki-67 antibody attaches to on a tissue sample, the more likely the tumor cells are to grow and divide rapidly. The result of this test is reported as the percentage of Ki-67-positive cells. It shows whether a low, moderate or high proportion of cancer cells are in the process of dividing.
Learn about proliferation rate information on a pathology report.
Learn about other factors that can affect treatment and prognosis.
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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