Breast Cancer

Your Pathology Report

Your pathology report is an essential document that provides information about the unique characteristics of your breast cancer. It serves as a guide for your health care team to plan the most effective treatment for your cancer based on its features.

Pathology reports may look different at different cancer centers and hospitals, but most of them include the same information. The details may seem overwhelming and you’ll likely encounter unfamiliar terms, but once you learn more, you’ll be better informed about your diagnosis and better able to discuss your treatment options with your doctor.

Your breast cancer diagnosis is most often based on the careful examination of a tissue biopsy from a suspected tumor or of the entire tumor after definitive surgery (removal of the tumor with or without lymph nodes). A pathology report is prepared by a pathologist (a physician with specialized training in determining the nature and cause of disease) after he or she has examined the specimen with and without a microscope, documenting its size, describing its appearance and sometimes performing special testing. The final diagnosis is based on all the findings of the examination and is included in your pathology report.

Diagnosing breast cancer and identifying all of the tumor’s characteristics are challenging tasks and require the expertise of physician specialists. The accuracy of testing and interpretation is essential because treatment is planned according to the final results. Getting a second opinion from another pathologist with extensive expertise in interpreting pathologic findings related to breast cancer can be beneficial, especially if there was any difficulty or controversy in interpreting the findings. Be sure to seek a second opinion if the pathology report does not contain a definite diagnosis, if you have a rare type of cancer, or if the cancer has already metastasized (spread). A second opinion can confirm your diagnosis or may suggest an alternative diagnosis.

The pathology report also includes the stage of the cancer. You will find more information about staging by clicking here.

Table 1. Components of a Pathology Report

Descriptor What is described or measured How result is reported What the finding means
Size Length and width of the tumor Largest dimension of the tumor, as measured in centimeters (1 inch = approximately 2.5 centimeters) Prognosis is likely to be better for smaller tumors; size is a primary factor in staging most cancers
Noninvasive vs. invasive Whether cancer cells are confined to a single cell layer or spread to nearby (or underlying) tissue Noninvasive cancer is termed "in situ" Prognosis is likely to be better for noninvasive cancer
Grade How closely the tumor cells resemble normal cells
Grade 1: well-differentiated (cancer cells look mostly similar to normal cells)
Grade 2: moderately differentiated (some cancer cells look different than normal cells)
Grade 3:  poorly differentiated (most cancer cells look different than normal cells)
Grade 4: undifferentiated (all cancer cells look different than normal cells)
The more the cancer cells look like normal cells, the better the prognosis; the higher the grade, the more aggressive the tumor
Surgical margins Presence or absence of cancer cells in the normal tissue surrounding the tumor (known as the margin)
Negative (or “not involved,” “clear” or “clean”): no cancer cells in the margin
Close: cancer cells are near the margin
Positive (or “involved”): cancer cells are in the margin
More surgery may be necessary if the margins are close or positive
Lymphovascular invasion Presence or absence of cancer cells in the blood or lymph vessels “Absent,” “Present,” “Extensive” Cancer cells present or extensive in the blood or lymph vessels suggest a more aggressive tumor
Lymph node status Presence or absence of cancer cells in the nearby lymph nodes
Negative: no cancer cells
Positive: cancer cells

For breast cancer, the lymph node status is expressed as the number of positive nodes/total number of nodes removed and examined
Negative lymph node status is generally associated with less extensive cancer and a better prognosis; lymph node status is another primary factor in staging
Proliferation rate (also known as Ki-67 proliferation index) Percentage of cancer cells that are actively dividing
<10%: favorable prognosis
10-20%: borderline prognosis
>20%: unfavorable prognosis
This index is not always determined and may not be a factor in treatment planning, as it is not a consistently reliable measurement that correlates with stage
Hormone receptor status (estrogen receptor [ ER] and progesterone receptor [ PR]) Expression of ER and PR on the cancer cells
ER-/PR- (negative): receptors absent or present on few cancer cells (usually less than 1%)
ER+/PR+ (positive): receptors present on a high proportion of cancer cells 
Positive tests for ER and/or PR indicate that the cancer is likely to respond to hormone therapy
HER2 status (also known as HER2/neu, c-erb-B2 or erb-2)
Presence of a protein produced by the HER2 gene on the surface of cancer cells (overexpression); or
Presence of extra copies of the gene (amplification)
When done by IHC (immunohistochemical analysis), 0 to +3, with 0, +1 and +2 being HER2- and +3 being HER2+
When done by FISH (fluorescent in situ hybridization), HER2- or HER2+
Presence of HER2 overexpression or amplification indicates a
fast-growing, aggressive tumor, but a HER2+ tumor is likely to respond to an anti- HER2 agent

Additional Resources