Your pathology report is an essential document that provides all the information about the unique characteristics of your breast cancer. The pathology report serves as a guide for your oncologist and other members of your health care team to plan the treatment that is most likely to be effective for your particular breast cancer.

Pathology reports may look different at different cancer centers and hospitals, but most include the same information. The details on a pathology report may seem overwhelming, especially because descriptions include unfamiliar terms. But once you learn more about what the words mean, you’ll be better informed about your diagnosis and thus be better able to discuss your diagnosis and treatment options with your doctor.

Your diagnosis of breast cancer is based on the careful examination of tissue obtained during the biopsy of 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 performing special testing (Table 1). The pathologist’s final diagnosis is based on all the findings of the examination.

Diagnosing breast cancer and identifying all of the characteristics of the tumor are challenging tasks and require the expertise of physician specialists. The accuracy of testing and interpretation of results is essential, as treatment is planned according to the final results. Getting a second opinion from another pathologist with extensive expertise in interpreting breast cancers can be of benefit, especially if there was difficulty or controversy in interpreting the findings. You should be sure to seek the opinion of another pathologist 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. Another pathologist’s interpretation can confirm your diagnosis or may suggest an alternative diagnosis.

The pathology report also includes the stage of the breast cancer. As with other cancers, breast cancer is classified in stages according to the system developed by the American Joint Committee on Cancer (AJCC). This tumor (T), node (N), metastasis (M) classification is then used as a foundation to assign a stage of 0 to IV (Table 2).

Table 1. Components of a Pathology Report on Breast Cancer

Descriptor	What is Described or Measured	How Result is Reported	What 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 (see Table 2)
Noninvasive vs. invasive	Whether cancer cells are confined to ducts or lobules or have spread to nearby breast tissue	Noninvasive cancer is termed in situ	Prognosis is likely to be better for noninvasive cancer
Histologic grade	How closely the tumor cells resemble normal cells	Grade 1: well-differentiated (cells look mostly similar to normal cells) Grade 2: moderately differentiated Grade 3: poorly differentiated (cells look very different from normal cells)	The more the cancer cells look like normal breast cells, the better the prognosis; the higher the grade, the more aggressive the tumor
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
Surgical margins	Presence or absence of cancer cells in the normal breast 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 needed if the margins are close or positive
Lymphovascular invasion	Presence or absence of cancer cells in the blood or lymph vessels		Cancer cells 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 Expressed as 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 (see Table 2)
Hormone receptor status (estrogen receptor [ER] and progesterone receptor [PR])	Expression of ER and PR on the cancer cells	ER / PR-: receptors present on no or low number of cancer cells ER/PR+: receptors present on a high proportion of cancer cells	Tumors positive for ER and/or PR indicates that the cancer is likely to respond to hormone therapy
HER2 status (also known as c-erb-2 or erb-2)	Presence of a protein produced by the HER2 gene on the cancer cells	When done by IHC, 0 to +3, with 0 and +1 being HER2- and +2 and +3 being HER2+ When done by FISH, HER2-or HER2+	Presence of HER2 indicates a fast-growing, aggressive tumor, but one that is likely to respond to an anti-HER2 agent < /td>

IHC = immunohistochemical analysis; FISH = fluorescent in situ hybridization.

Table 2. Stages of Breast Cancer

Stage	Description*
Early-Stage Breast Cancer
Stage 0	Noninvasive breast cancer (ductal carcinoma in situ)
Stage 1	Small tumor that has not spread to lymph nodes
Stage IIA	Small tumor that has spread to 1-3 axillary lymph nodes (nodes in the armpit) OR Medium tumor that has not spread to lymph nodes OR No evidence of breast tumor but presence of cancer cells in the axillary lymph nodes
Later-Stage Breast Cancer
Stage IIB	Medium tumor that has spread to 1-3 axillary lymph nodes OR Large tumor that has not spread to lymph nodes
Stage IIIA	Small or medium tumor that has spread to 1-3 axillary lymph nodes OR Large tumor that has spread to 1-9 lymph nodes OR Any size tumor that has spread to 10 lymph nodes or more
Stage IIIB (locally advanced)	Tumor that extends to the chest wall, with swelling, ulceration that has not spread to nearby lymph nodes
Stage IIIC	Any size tumor that has spread to 10 or more nearby nodes
Advanced (Metastatic) Breast Cancer
Stage IV	Any size tumor, with or without spread to nearby lymph nodes, that has spread to other organs (most notably, bone, lungs, or liver)

*Small = tumors up to 2 centimeters; medium = tumors more than 2 centimeters but less than 5 centimeters; large = tumors more than 5 centimeters.

Stage is based on the classification system developed by the American Joint Committee on Cancer (AJCC).

Additional Sources of Information

Breast Cancer Network of Strength: www.networkofstrength.org
Understanding Your Breast Cancer Pathology Report
BreastCancer.org: www.breastcancer.org
Your Diagnosis
Living Beyond Breast Cancer: www.lbbc.org
Guide for the Newly Diagnosed
Susan G. Komen for the Cure: ww5.komen.org
Diagnosis