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Pathology FAQ: Breast Cancer


When your breast was biopsied, the samples taken were studied under the microscope by a specialized doctor with many years of training called a pathologist. The pathology report tells your treating doctor the diagnosis in each of the samples to help manage your care. This FAQ sheet is designed to help you understand the medical language used in the pathology report.

1. What is “carcinoma” or “adenocarcinoma”?

Breast carcinoma or adenocarcinoma is synonymous with breast cancer, which is malignant. However, it can be curable when caught early.

2. What is “infiltrating” or “invasive”?

These words mean the same. The normal breast is made of ducts that end in a group of blind-ending sacs (lobules). Carcinomas start out in the ducts and lobules and when they grow and break out of these structures and are no longer confined to the breast ducts or lobules, they are considered invasive or infiltrating carcinoma, which means that the tumor cells now have the potential to spread (metastasize) to other parts of your body.

3. What does it mean if my carcinoma is called “ductal” or “lobular” or “carcinoma with duct and lobular features”?

Breast carcinomas have different appearances under the microscope, the two major types being ductal carcinoma or lobular carcinoma. In some cases, the tumor can have features of both and are called mixed ductal and lobular carcinoma. In general, there is not a significantly different prognosis between invasive lobular and invasive ductal adenocarcinoma of the breast.

4. What does it mean if my report mentions E-cadherin?

E-cadherin is a test that the pathologist may use to help determine if the tumor is ductal or lobular. If your report does not mention E-cadherin, it means that this test was not necessary to make the distinction.

5. What does it mean if my carcinoma is well-differentiated, moderately-differentiated, or poorly differentiated”?

These terms are used to indicate how aggressive your carcinoma is likely to be. They are assigned by a pathologist looking at the cancer under the microscope. Well-differentiated carcinomas tend to be more slowly growing, with a better prognosis. Poorly-differentiated carcinomas are more aggressive tumors, with a worse prognosis, while moderately-differentiated carcinomas are in the middle.

6. What is “histologic grade” or “Nottingham grade”?

These grades are similar to what is described in FAQ 5 above, about “differentiation”. Numbers are assigned to different features seen under the microscope and then added up to assign the grade. The added numbers range from 3 to 9, with 3-5 equal to grade 1 (well-differentiated), 6-7 equal to grade 2 (moderately differentiated), and 8-9 equal to grade 3 (poorly differentiated). In some reports, the grade may be similarly described as Elston grade.

7. What does it mean if Ki67 is mentioned in my report?

Ki67 is a measurement of the cancer cell proliferation rate, which the pathologist determines under the microscope. The proliferation rate is a measure of how rapidly the cancer cells are dividing, another indicator of prognosis.

8. What does it mean if my carcinoma has “tubular”, “mucinous”, “cribriform”, or “micropapillary” features?

These terms mostly describe the arrangement of cells in an invasive or in situ cancer. Tubular cancers are easy to treat and have a low risk of recurrence. Mucinous cancers produce mucous and often have a better prognosis than most other types of breast cancer. Beyond that, these descriptive terms contribute little or nothing to treatment planning.

9. What is “vascular” or “lymphovascular” or “angiolymphatic” invasion? What if my report mentions D2-40 (podoplanin) or CD34?

Tumors cells can break into small vessels seen under the microscope and this is called “vascular” or “lymphovascular invasion”. The presence of tumor in vessels is associated with an increased risk that the tumor has spread outside the breast, although this does not always occur. D2-40 and CD34 are special tests that the pathologist may use to help identify “vascular” or “lymphovascular” or “angiolymphatic” invasion. These tests are not necessary in every case. If your report does not mention this type of invasion, it means it is not present. Even if it is present, your cancer could still be very curable, depending on other factors. How the presence of this finding will affect your specific treatment is best discussed with your treating doctor.

10. What is the significance of the reported size of the tumor?

The pathologist typically will measure the greatest dimension of the tumor as seen under the microscope or, if it is visible, by gross (naked eye) examination. A size will sometimes be included on a pathology report from a core biopsy. This is not a reliable estimate of the true size of the tumor. The most accurate size measurement will come from the excised tumor after lumpectomy or mastectomy.

11. What is the significance of the stage of the tumor?

Stage is a measure of how advanced a tumor is. It is based on tumor size and evidence of tumor outside of the breast. A clinical stage is assigned prior to surgery based on clinical exam and imaging. A final pathologic stage, designated by the letter “p”, is determined after surgery. The TNM system is commonly used to calculate stage. In this system “T” stands for tumor size, “N” for spread into lymph nodes and “M” for spread into other organs. There are criteria, including information not always on the pathology report, to group TNM stages into 5 major stage groups, 0 to IV, correlating with increasing extent of disease and poorer prognosis. Detailed information on Staging is present at the American Cancer Society and at the American Joint Committee on Cancer  “staging resources”. How the stage of your tumor will affect your therapy is best discussed with your treating physician.

12. What if my report mentions “sentinel lymph node”?

This FAQ concerns itself with the explanation of pathologic terms in breast biopsies. Information regarding breast cancer lymph nodes, including rationale for “sentinel lymph node” biopsy, can be found at the following websites:

13. What does it mean if my report mentions special studies such as high molecular weight cytokeratin (HMWCK), CK903, CK5/6, p63, muscle specific actin, smooth muscle myosin heavy chain, calponin, or keratin?

These are special tests that the pathologist sometimes uses to help make the diagnosis of invasive breast cancer or to identify metastatic cancer in lymph nodes. Not everyone needs these tests. Whether your report does or does not mention these tests has no bearing on the accuracy of your diagnosis.

14. What does it mean if my report also has any of the following terms: “usual duct hyperplasia”, “adenosis”, “sclerosing adenosis”, “radial scar”, “complex sclerosing lesion”, “papillomatosis”, “papilloma”, “apocrine metaplasia”, “cysts”, “columnar cell change”, “collagenous spherulosis”, “duct ectasia”, “fibrocystic changes”, “flat epithelial atypia”, or “columnar cell change with prominent apical snouts and secretions (CAPSS)”?

All of these terms are non-cancerous changes that the pathologist sees under the microscope and are of no importance when seen on a biopsy where there is cancer.

15. What does it mean if my report mentions “microcalcifications” or “calcifications”?

“Microcalcifications” or “calcifications” are minerals that are found in both noncancerous and cancerous breast lesions and can be seen both on mammograms and under the microscope. Because some calcifications are associated with cancerous lesions, their presence on a mammogram may lead to a biopsy of the area. When they are seen by the pathologist in a biopsy specimen which was obtained because of a mammographic abnormality with calcifications, their presence is included in the pathology report to let the treating physician know that the abnormal area with calcifications seen in the mammogram was successfully sampled. Without accompanying worrisome changes in the breast ducts or lobules, “microcalcifications” or “calcifications” alone have no significance.

16. What does it mean if in addition to cancer my report also mentions “atypical duct hyperplasia (ADH)”, “atypical lobular hyperplasia (ALH)”, “ductal carcinoma in-situ (DCIS)”, “intraductal carcinoma”, “lobular carcinoma in-situ (LCIS)”, or “in-situ lobular carcinoma”?

All of these terms, some synonymous, are pre-cancerous changes, that the pathologist sees under the microscope. These are typically of no importance when seen on a needle biopsy.

17. What does it mean if my report mentions “estrogen receptor (ER)” or “progesterone receptor (PR)”?

ER and PR are special tests that the pathologist does that are important in predicting response of the cancer to certain types of therapy. Women have circulating estrogen and progesterone in their blood, and some cancers might grow more readily if the circulating estrogen and progesterone attach to these receptors. If these receptors are present in the cancer, your treating physician may explore with you the possibility of using drugs that block these receptors. Results for ER and PR are reported separately and can be reported in different ways: 1) negative, weakly positive, positive; 2) percent positive; 3) percent positive and whether the staining is weak, moderate, or strong. How the results of your tests will affect your therapy is best discussed with your treating physician.

18. What if my report mentions HER2/neu?

Some breast cancers (about 15 – 20%) have on the surface of the cancer cells a protein called HER2/neu. HER2/neu is a special test done by pathologists that is predictive of both the prognosis and the response of breast cancer to certain types of therapy. HER-2/neu may be tested in breast cancer using a technique called immunohistochemistry (IHC). In that case, the result is typically reported as 0 (negative), 1+ (also negative), 2+ (equivocal), and 3+ (strongly and diffusely positive). Equivocal tests (2+) are followed up with a testcalled fluorescence in situ hybridization (FISH). A FISH test is reported as Negative, Positive, or Equivocal. If your HER-2/neu test is positive, your treating physician may choose a different set of drugs to treat the breast cancer. How the results of your tests will affect your therapy is best discussed with your treating physician.

19. What if my report mentions “margins” or “ink”?

When an excisional biopsy (lumpectomy) of a breast cancer is performed, the pathologist coats the outer aspect of the specimen with ink, sometimes different colored ink. If cancer extends to the ink, it indicates that it may not have been completely removed (i.e., it is at the surgical “margin”). However, the surgeon may have removed additional tissue at the time of surgery to guard against this possibility. The management of “invasive carcinoma”, “intraductal carcinoma” (pre-cancer), “in-situ lobular carcinoma” (pre-cancer), “atypical duct hyperplasia”(early pre-cancer), or “atypical lobular hyperplasia (early pre-cancer)” at a margin is best discussed with your treating physician.

Navigate our Pathology FAQs and Images

  1. Benign Breast FAQ
  2. Benign Diseases - Atlas of Images
  3. Atypical Hyperplasia
  4. Breast Cancer In-Situ
  5. Breast Cancer
  6. Malignant Tumors - Atlas of Images
  7. Ask an Expert - Understanding Pathology Results

Authors: Jeanne Simpson (Vanderbilt Medical Center), Stuart Schnitt (Beth Israel Deaconess Medical Center), Jonathan I. Epstein (Johns Hopkins Medical Institutions)