Your doctor will order a series of tests on the cancer and nearby tissues to create a “profile” of how the breast cancer looks and behaves. Some of these tests are done after the initial biopsy (removal of tissue sample for testing), others in the days and weeks after lumpectomy or mastectomy. Each time testing is done, your doctor receives a report of results from the laboratory.
All of these lab reports together make up your complete pathology report.
Your pathology report is so important because it provides information you and your doctor need to make the best treatment choices for your particular diagnosis. Those decisions depend on knowing characteristics such as:
the size and appearance of the cancer
how quickly it grows
any signs of spread to nearby healthy tissues
whether certain things inside the body — such as hormones or genetic mutations (abnormal changes in genes) — are factors in the cancer’s growth and development
Getting Your Pathology Report
Because parts of your pathology report results will come back over time, we suggest these two important tips:
Wait for the whole picture.
Some tests take longer than others, and not all tests are done by the same lab. In the few weeks after surgery, you may see a few different reports from different labs.
Waiting can be very difficult, and it may be tempting to fixate on each piece of information by itself. However, you and your doctor need the complete pathology report to truly understand the cancer and decide on a treatment plan. Ask your doctor how and when you can get the results and discuss them together (the language in the reports is technical and not always reader-friendly). Call the office if you are expecting a result but haven’t heard anything.
Keep all pathology report results in one place.
You will need those results as you learn more about your diagnosis, consider treatment options, and meet with your medical team.
Non-Invasive or Invasive Breast Cancer
Breast cancer usually begins either in the cells of the lobules, which are milk-producing glands, or the ducts, the passages that drain milk from the lobules to the nipple. The pathology report will tell you whether or not the cancer has spread outside the milk ducts or lobules of the breast where it started.
Non-invasive cancers stay within the milk ducts or lobules in the breast. They do not grow into or invade normal tissues within or beyond the breast.Non-invasive cancers are sometimes called carcinoma in situ (“in the same place”) or pre-cancers.
Invasive cancers do grow into normal, healthy tissues. Most breast cancers are invasive.
Whether the cancer is non-invasive or invasive will determine your treatment choices and how you might respond to the treatments you receive.
In some cases, a breast cancer may be both invasive and non-invasive. This means that part of the cancer has grown into normal tissue and part of the cancer has stayed inside the milk ducts or milk lobules. It would be treated as an invasive cancer.
A breast cancer also may be a “mixed tumor,” meaning that it contains a mixture of cancerous ductal cells and lobular cells. This type of cancer is also called “invasive mammary breast cancer” or “infiltrating mammary carcinoma.” It would be treated as a ductal carcinoma.
If there is more than one tumor in the breast, the breast cancer is described as either multifocal or multicentric. In multifocal breast cancer, all of the tumors arise from the original tumor, and they are usually in the same section of the breast. If the cancer is multicentric, it means that all of the tumors formed separately, and they are often in different areas of the breast.
In most cases, you can expect the breast cancer to be classified as one of the following.
DCIS (Ductal Carcinoma In Situ): DCIS is a non-invasive cancer that stays inside the milk duct.
LCIS (Lobular Carcinoma In Situ): LCIS is an overgrowth of cells that stay inside the lobule. It is not a true cancer; rather, it is a warning sign of an increased risk for developing an invasive cancer in the future in either breast.
IDC (Invasive Ductal Carcinoma): The most common type of breast cancer, invasive ductal carcinoma begins in the milk duct but has grown into the surrounding normal tissue inside the breast.
Less Common Subtypes of Invasive Ductal Carcinoma can include tubular, medullary, mucinous, papillary, and cribriform carcinomas of the breast. In these cancers, the cells can look and behave somewhat differently than invasive ductal carcinoma cells usually do.
ILC (Invasive Lobular Carcinoma): ILC starts inside the lobule but grows into the surrounding normal tissue inside the breast.
Inflammatory Breast Cancer: Inflammatory breast cancer is a fast-growing form of breast cancer that usually starts with the reddening and swelling of the breast, instead of a distinct lump.
Male Breast Cancer: Breast cancer in men is rare, but when it occurs, it is almost always a ductal carcinoma.
Paget’s Disease of the Nipple: Paget’s disease of the nipple is a rare form of breast cancer in which cancer cells collect in or around the nipple.
Phyllodes Tumors of the Breast: Phyllodes tumors are rare breast tumors that begin in the connective tissue of the breast (stroma) and grow quickly in a leaflike pattern. Some are cancerous, but most are not.
Recurrent and/or Metastatic Breast Cancer: Breast cancer that has returned after previous treatment or has spread beyond the breast to other parts of the body.
Grade is a “score” that tells you how different the cancer cells’ appearance and growth patterns are from those of normal, healthy breast cells. Your pathology report will rate the cancer on a scale from 1 to 3:
Grade 1 or low grade (sometimes also called well differentiated): Grade 1 cancer cells look a little bit different from normal cells, and they grow in slow, well-organized patterns. Not that many cells are dividing to make new cancer cells.
Grade 2 or intermediate/moderate grade (moderately differentiated): Grade 2 cancer cells do not look like normal cells and are growing and dividing a little faster than normal.
Grade 3 or high grade (poorly differentiated): Grade 3 cells look very different from normal cells. They grow quickly in disorganized, irregular patterns, with many dividing to make new cancer cells.
Having a low-grade cancer is an encouraging sign. But keep in mind that higher-grade cancers may be more vulnerable than low-grade cancers to treatments such as chemotherapy and radiation therapy, which work by targeting fast-dividing cells.
Be careful not to confuse grade with stage, which is usually expressed as a number from 0 to 4 (often using Roman numerals I, II, III, IV). Stage is based on the size of the cancer and how far it has (or hasn’t) spread beyond its original location within the breast.
Rate of Cell Growth
Your pathology report may include information about the rate of cell growth — what proportion of the cancer cells within the tumor are growing and dividing to form new cancer cells.
A higher percentage suggests a faster-growing, more aggressive cancer, rather than a slower, “laid back” one. Tests that can measure the rate of growth include:
S-phase fraction: This number tells you what percentage of cells in the sample are in the process of copying their genetic information, or DNA. This S-phase, short for “synthesis phase,” happens just before a cell divides into two new cells. A result of less than 6% is considered low, 6-10% intermediate, and more than 10% is considered high.
Ki-67: Ki-67 is a protein in cells that increases as they prepare to divide into new cells. A staining process can measure the percentage of tumor cells that are positive for Ki-67. The more positive cells there are, the more quickly they are dividing and forming new cells. In breast cancer, a result of less than 10% is considered low, 10-20% borderline, and high if more than 20%.
Although the S-phase fraction and Ki-67 level may provide you and your doctor with useful information, experts don’t yet agree on how to use the results when making treatment decisions. Therefore, not all doctors order these tests routinely, so they may not appear in your pathology report. The other results in your report will be much more important in making informed choices. (If you decide to have an Oncotype DX test to check the likelihood of cancer coming back and whether you could benefit from chemotherapy, Ki-67 will be included in that panel of testing.)
The surgeon’s goal during surgery is to take out all of the breast cancer along with rim of normal tissue around it. This is to be sure that all of the cancer has been removed.
During or after surgery, a pathologist examines this rim of tissue — called the surgical margin or margin of resection — to be sure it’s clear of any cancer cells. If cancer cells are present, this will influence decisions about treatments such as additional surgery and radiation. Margins are checked after surgical biopsy, lumpectomy, and mastectomy.
Your pathology report may say that the surgical margins are:
Clear (also called Negative or Clean): No cancer cells are seen at the outer edge of the tissue that was removed (the tumor along with the rim of surrounding tissue). Sometimes the pathology report also will tell you how wide the clear margin is — the distance between the outer edge of the surrounding tissue removed and the edge of the cancer. When margins are clear, usually no additional surgery is needed.
Positive: Cancer cells come right out to the edge of the removed tissue. More surgery is usually needed to remove any remaining cancer cells
Close: Cancer cells are close to the edge of the tissue, but not right at the edge. More surgery may be needed.
An important note: There is not a standard definition of how wide a “clear margin” has to be. In some hospitals, doctors want 2 millimeters (mm) or more of normal tissue between the edge of the cancer and the outer edge of the removed tissue. In other hospitals, though, doctors consider a 1-mm rim of healthy tissue — and sometimes even smaller than that — to be a clear margin. As you talk with your doctor about whether your margins were clear, positive, or close, you also can ask how “clear” is defined by your medical team.
Size of the Breast Cancer
Size indicates how large across the tumor is at its widest point. Doctors measure cancer in millimeters (1 mm = .04 inch) or centimeters (1 cm = .4 inch). Size is used to help determine the stage of the breast cancer.
Size doesn’t tell the whole story, though. All of the cancer’s characteristics are important. A small cancer can be aggressive while a larger cancer is not — or it could be the other way around.
Lymph Node Involvement
Before or during surgery to remove an invasive breast cancer, your doctor removes one or some of the underarm lymph nodes so they can be examined under a microscope for cancer cells. The presence of cancer cells is known as lymph node involvement.
Lymph nodes are small, bean-shaped organs that act as filters along the lymph fluid channels. As lymph fluid leaves the breast and eventually goes back into the bloodstream, the lymph nodes try to catch and trap cancer cells before they reach other parts of the body. Having cancer cells in the lymph nodes under your arm suggests an increased risk of the cancer spreading.
When lymph nodes are free, or clear, of cancer, the test results are negative. If lymph nodes have some cancer cells in them, they are called positive. Your pathology report will tell you how many lymph nodes were removed, and of those, how many tested positive for the presence of cancer cells. For example, 0/3 means 3 nodes were removed and 0 were positive, while 2/5 means 5 were removed and 2 were positive.
Your results will also tell you how much cancer is in each node — ranging from a few tiny cells to many cells that can be seen easily. You might see this reported as:
Microscopic (or minimal): Only a few cancer cells are in the node. A microscope is needed to find them.
Gross (also called significant or macroscopic): There is a lot of cancer in the node. You can see or feel the cancer without a microscope.
Extracapsular extension: Cancer has spread outside the wall of the node.
The more lymph nodes that contain cancer cells, the more serious the cancer might be. So doctors use the number of involved lymph nodes to help make treatment decisions.
Vascular or Lymphatic System Invasion
The breast has a network of blood vessels (called the vascular system) and lymph channels (lymphatic system) that carry blood and fluid back and forth from your breast tissue to the rest of the body. They are the “highways” that bring in nourishment and remove used blood and the waste products of cell life.
Vascular or lymphatic system invasion happens when breast cancer cells break into the blood vessels or lymph channels. This increases the risk of the cancer traveling outside the breast or coming back in the future. Doctors can recommend treatments to help reduce this risk.
Your pathology report will say “present” if there is evidence of vascular or lymphatic system invasion. If there is no invasion, your report will say “absent.” Lymphatic invasion is different from lymph node involvement. The lymph channels and lymph nodes are part of the same system, but they are looked at and reported separately.