Understanding Pathology Results

Most of the important information about your breast cancer will come from your pathology report. This information can be overwhelming, but understanding what it means can help you feel more confident and hopeful.

Your Breast Cancer Pathology Report

The pathology report describes what the pathologist sees when looking at your tissue sample, which comes from your biopsy or surgery, under a microscope. This page will help you better understand the major parts of your pathology report so you know what to expect from your doctor’s explanation.

Gross description is what the pathologist sees when looking at the tissue and may include color, size and part of the breast from which the tissue came.

Your pathology tells you where the cancer began (duct or lobe of breast) and whether it is contained (in situ) or has invaded surrounding tissue (invasive).

Size describes how big the tumor is, usually measured in centimeters or millimeters.

Location describes where in the breast the tumor is located, usually described as a quadrant or section of the breast.

Histologic grade describes how quickly the tumor cells are dividing. Based on microscope images, doctors give a grade number from “one” (slow division) to “three” (fast division), providing a measure of how aggressive the cancer is. You may also see the tumor grade described as “differentiation” on your pathology report. A grade 1 tumor is “well differentiated,” because the cancer cells look similar to normal cells. A grade 2 tumor is “moderately differentiated,” and a grade 3 tumor is “poorly differentiated,” because it looks very unlike normal cells.

Proliferation rate provides more information about how fast the cancer cells are dividing. Doctors commonly use a measure called “Ki-67” to describe the proliferation rate. A low Ki-67 percentage means slowly dividing cells, and a high Ki-67 (over 20%) means quickly dividing cells. Do not be alarmed if your pathology report does not contain this information or if your rate is high. There is no conclusive evidence that Ki-67 is associated with survival. For this reason, not all pathology reports will contain this score.

Hormone receptor status describes how sensitive your cancer cells are to the hormones estrogen and progesterone. If cancer cells have the specific receptors, these hormones can attach and give instructions to the cells to grow and divide. Doctors measure this status as a positive or negative, and sometimes a percent is also provided (e.g., 90% estrogen receptor positive).

HER2/neu (Human Epidermal Growth Factor Receptor 2) status describes how sensitive your cancer cells are to the human epidermal growth factor receptor protein, which is important for cancer growth and division. If your cancer cells have excess amounts of this receptor, they can receive more messages to grow. Doctors measure the amount of this receptor in terms of positive and negative status—a positive status means your cells have more receptor protein. Pathologists test for HER2 status because there are drugs available that target the HER2 receptor. There are two ways to test for HER2 status, which you may see reported. The immunohistochemistry (IHC) test results in a score from 0 to 3. Zero and 1 are a negative result, and 3 is a positive result. A 2 indicates that the result is unclear and further testing may be needed. The FISH (fluorescence in situ hybridization) test gives a positive (HER2 is overexpressed) or negative result.

Lymphovascular invasion describes whether breast cancer cells have entered blood vessels or lymph nodes. From these sites, the cancer can spread to other parts of the body.

Lymph node test results describe how many lymph nodes had breast cancer cells in them. Lymph nodes are an important part of your immune system. During surgery, doctors remove some lymph nodes and examine them for cancer cells. They count how many have cancer (also called “positive” for cancer). Doctors learn more about the potential spread of your cancer by the number of lymph nodes that were positive for cancer.

Surgical margin results describe whether all of a tumor was removed during surgery. Surgeons cut out additional tissue surrounding a tumor during surgery. This is called the “surgical margin.” They test the margin tissue to see if it contains cancer cells. If there are no cancer cells at the edge of the tissue specimen, it is said to be a “clean” or “clear” margin. A “close” margin means that cancer cells were found close to the edge of the tissue. A margin that is close or not clear/clean may mean that an additional surgery is required to remove the rest of the tumor.

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