Understanding Your Pathology Report

The pathology report is the document that provides all of the information about your breast cancer, based on the tissue the surgeon removes and sends to the pathologist for examination.  Pathology reports contain a great deal of clinical information and can be complicated and hard to understand.  This section describes the categories of information you will find on your pathology report and what it means.  You should request a copy of this report – and of all laboratory tests and procedures – and discuss it with your doctor.

In making the diagnosis of breast cancer, doctors usually perform a number of tests.  The results may not all be available at the same time.  Some tests may be run by laboratories outside of the hospital and therefore, it may take longer to get those results.  Some terms you may see on your pathology report include:

Gross description: This explains the tissue sample that is being examined.  It includes where the tissue comes from, its size, and its weight, plus any other features noted by the pathologist.  The size of the tumor is recorded in centimeters.

Invasive or non-invasive: Invasive (also called infiltrating) means the cancer cells have broken through the wall of either the milk duct or the lobule.  Most breast cancers are invasive.  Those that are not are called in situ, meaning that they are literally "in place," confined to the duct or lobule where they began.  Some breast cancers are mixed tumors, meaning that some areas are both invasive and non-invasive.  Breast cancers can also be multifocal, meaning that they appear in more than one place in the breast.  They may or may not be the same kind of tumor.

Grade: Pathologists use a scale known as the Bloom-Richardson or Scarff-Bloom-Richardson scale to assign a histologic grade to the tumor.  This score combines information about three factors that influence the growth rate of the cancer cells and describes the extent to which the cells resemble, or have ceased to resemble normal breast cells in their appearance, and behavior. 

Surgical margins: The surgeon's goal is to remove the entire known tumor with a "clear margin," or non-cancerous tissue around it.  Having a clear (or negative) surgical margin reduces the risk that the tumor will recur, especially in the area in which it originated.  A positive margin may indicate the need for additional surgery.

Lymph node status: The surgeon may remove one or more lymph nodes from your armpit, the axilla.  If the surgeon does an axillary lymph node dissection, the pathology report will list the number of nodes positive for cancer of the total number of nodes removed.  For example, 0/9 means none of the nine nodes that were removed were positive, and 3/12 indicates that cancer was found in three of 12 nodes.

Hormone receptor status: The pathologist will determine whether your cancer has receptors for estrogen (ER+/-) and progesterone (PR+/-) .  The determination is often more complicated than just a positive or negative.  It uses one of several available scoring systems that assign a numerical ranking based on the percentage of cancer cells that are positive for hormone receptors.  Hormone receptor status is very important in determining treatment because it can influence what kind of treatment will be recommended for you.

HER2 status: Several tests can be used to measure whether or not your HER2 status is amplified.  If your doctor uses the ImmunoHistoChemistry (IHC) test, the results will be reported as positive, negative, or borderline.  If the Fluorescence in situ Hybridization (FISH) test is used, the results will be reported as positive (indicating amplified), or negative (not amplified).  A third test, SPoT-Light HER2 CISH, also reports status as positive for amplified, or negative for not amplified.  HER2+ tumors are generally faster growing and more aggressive, but can also be treated with therapies targeted to the HER2 gene.

Lymphovascular invasion: This is the penetration of cancer cells into the interior of the blood vessels or lymphatic channels, often seen in small clusters under the microscope.  Lymphovascular invasion may indicate a more aggressive tumor.  Note that it is not the same as lymph node status.

Rate of cell growth: The pathology report may include information about the rate of cell growth; that is, the proportion of cancer cells within the tumor that are actively growing and dividing.  A higher percentage suggests a more aggressive, faster growing cancer.  The two most common tests used for this purpose are known as S-Phase Fraction and Ki-67.

Genomic Assays (Oncotype DX and MammaPrint): Genomic assays are a relatively new type of test that analyzes the breast tumor for the activity of a group of genes that can help predict the risk of whether that breast cancer will recur either locally or distantly.  They provide important information on the value of chemotherapy, preventing unnecessary side effects in patients who have a low likelihood of recurrence or response to chemotherapy.  Two such tests are currently in use, Oncotype DX (which investigates 21 genes) and MammaPrint (which considers 70 genes), with others under development.