Breast Cancer

Staging

After you receive your diagnosis, staging will be a topic of conversation you have with many people. For your doctor, it will help determine how the cancer might behave and, as a result, how best to treat it. For your loved ones, it may help them understand your diagnosis. This section will help you understand why your cancer received the stage it did and how it will affect your treatment plan.

All types of breast cancer are classified according to the tumor, node, metastasis (TNM) system developed by the American Joint Committee on Cancer (AJCC) (see Table 1). Once classified, they are given a stage that is described using Roman numerals from 0 to IV and the letters A, B or C, if applicable (see Table 2).

At first glance, the classification and staging tables may be confusing, but they are included so you can find your unique diagnosis. Once you know your stage and locate the corresponding example in the breast cancer illustrations, they may be easier to understand.

Explaining T, N and M

The T classification categories are the same for both clinical and pathologic staging and provide information on the size and extent of the tumor within the breast. Clinical T (described as cT) refers to the tumor size estimate based on physical/clinical examination and breast imaging; pathologic T (described as pT) refers to the size of the tumor when it has been removed and measured in the pathology laboratory.

Clinical staging for the N category (cN) describes the location and bulkiness of lymph nodes (usually in the axilla, under the arm) that seem to be malignant (from spread of the breast cancer) upon physical examination. Location and extent of any cancerous lymph nodes provide clues regarding the likelihood that the breast cancer might have spread to other organs. The pathologic N category (pN) is determined postoperatively and describes how many lymph nodes are involved.

The M category indicates if the cancer has metastasized, or spread, to another part of the body beyond the breast and nearby lymph nodes.

Additional Staging Considerations

Many other important factors are considered (and documented on your pathology report) before you receive your final stage: tumor grade; biomarkers, including your estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2) status (see Molecular testing offers insight into your treatment plan, below); molecular and genetic changes in cancer tissue; and results from multi-gene panels such as MammaPrint, Oncotype DX, PAM 50 (Prosigna) and Breast Cancer Index.

Ongoing tests in these areas to monitor the cancer and its treatment or disease progression may yield different results. In that case, the cancer may be restaged and the treatment plan modified accordingly. This may be a good time to seek a second opinion from a specialist experienced in treating breast cancer. Another opinion can confirm the treatment plan or offer new options.

Ask your doctor to write down your stage and to give you a copy of your pathology report for your records. Having a record of this information not only helps you and your loved ones have a better understanding of your diagnosis, it is a valuable resource if you are considering a clinical trial and need to determine if you meet eligibility criteria.

Molecular Testing Offers Insight Into Your Treatment Plan

Diagnosing breast cancer begins with imaging tests, a biopsy and blood tests. Because most cancers are caused by mutations, which are changes that occur in DNA, molecular testing, including both genomic and genetic testing, may be performed.

Genomic testing examines a cancer’s genes, which may reveal mutations that could indicate the cancer’s behavior, how aggressive it might be and if it will metastasize (spread). It is used to detect biomarkers, which are substances such as genes or molecules that can be measured in the blood, plasma, urine, cerebrospinal fluid or other body fluids or tissues.

Estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER2) are considered biomarkers in breast cancer. If the cancer is ER+ or PR+, it is driven by hormones. As a result, hormone (endocrine) therapy designed to block the hormones that feed the cancer may be used. If the cancer has too many copies of the HER2 gene or there are too many HER2 receptors, the cancer is HER2+ and may be treated with certain types of targeted therapy. The cancer is considered triple positive breast cancer if it is ER+, PR+ and HER2+.

Genetic testing looks for cancer-causing mutations that are inherited from your parents’ germ cells (egg and sperm cells that form an embryo), or that are acquired, which means they develop over time. Inherited mutations are also known as germline mutations, and acquired mutations are also known as somatic mutations.

Testing will likely be performed to determine if you carry a gene that raises the risk for developing cancer, especially if there is a history of certain cancers in your family. The breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) genes are the most commonly tested for, and your doctor may include others.

Having an inherited mutation doesn’t mean you will automatically develop cancer; it only means the risk is increased and you can explore ways to lower the risk, such as preventive surgery, medication, frequent screenings or lifestyle changes. Risk factors include the following:

  • Family history of any cancer, rare cancers and male breast cancer
  • Cancer at an early age
  • Multiple cancers in one relative
  • Ancestry, such as Ashkenazi Jewish heritage

Choosing to get genetic testing is a decision that affects your entire family. Knowing and sharing the information could help them be screened and monitored closely if they have a gene mutation associated with cancer. Preventing or detecting a cancer early offers the best chance of a successful treatment outcome.

Table 1. Stages of Breast Cancer

Stage TNM Classification
0 Tis, N0, M0
IA T1, N0, M0
IB T0 or T1, N1mi, M0
IIA T0 or T1, N1, M0
T2, N0, M0
IIB T2, N1, M0
T3, N0, M0
IIIA T0-T3, N2, M0
T3, N1, M0
IIIB T4, N0-N2, M0
IIIC Any T, N3, M0
IV Any T, Any N, M1

Table 2. TNM System for Classifying Breast Cancers

Category Definition
Tumor (T)
TX Primary tumor cannot be assessed.
T0 No evidence of primary tumor.
Tis (DCIS) Ductal carcinoma in situ.
Tis (Paget) Paget disease of the nipple NOT associated with invasive carcinoma and/or carcinoma in situ (DCIS) in the underlying breast parenchyma (tissue).
T1
  T1mi
  T1a
  T1b
  T1c
Tumor ≤ (not more than) 20 mm in greatest dimension.
Tumor ≤ (not more than) 1 mm in greatest dimension.
Tumor > (more than) 1 mm but ≤ (not more than) 5 mm in greatest dimension.
Tumor > (more than) 5 mm but ≤ (not more than) 10 mm in greatest dimension.
Tumor > (more than) 10 mm but ≤ (not more than) 20 mm in greatest dimension.
T2 Tumor > (more than) 20 mm but ≤ (not more than) 50 mm in greatest dimension.
T3 Tumor > (more than) 50 mm in greatest dimension.
T4

  T4a
  T4b

  T4c
  T4d
Tumor of any size with direct extension to the chest wall and/or to the skin (ulceration or macroscopic nodules).
Extension to the chest wall.
Ulceration and/or ipsilateral (on the same side) macroscopic satellite nodules and/or edema (including peau d’orange) of the skin that does not meet the criteria for inflammatory carcinoma.
Both T4a and T4b are present.
Inflammatory carcinoma.
Node (N)
pNX Regional lymph nodes cannot be assessed.
pN0
  pN0(i+)

  pN0(mol+)
No regional lymph node metastasis identified or ITCs (isolated tumor cells) only.
ITCs (isolated tumor cells) only (malignant cell clusters no larger than 0.2 mm) in regional lymph node(s).
Positive molecular findings by reverse transcriptase polymerase chain reaction (RT-PCR); no ITCs (isolated tumor cells) detected.
pN1


  pN1mi
  pN1a
  pN1b
  
  pN1c
Micrometastases; or metastases in 1-3 axillary (armpit) lymph nodes; and/or clinically negative internal mammary nodes with micrometastases or macrometastases by sentinel lymph node biopsy.
Micrometastases (approximately 200 cells, larger than 0.2 mm, but none larger than 2.0 mm).
Metastases in 1-3 axillary (armpit) lymph nodes, at least one metastasis larger than 2.0 mm.
Metastases in ipsilateral (on the same side) internal mammary sentinel nodes, excluding ITCs (isolated tumor cells).
pN1a and pN1b combined.
pN2
  
  pN2a
  pN2b
Metastases in 4-9 axillary (armpit) lymph nodes; or positive ipsilateral (on the same side) internal mammary lymph nodes by imaging in the absence of axillary lymph node metastases.
Metastases in 4-9 axillary (armpit) lymph nodes (at least one tumor deposit larger than 2.0 mm).
Metastases in clinically detected internal mammary lymph nodes with or without microscopic confirmation; with pathologically negative axillary (armpit) nodes.
pN3






  pN3a
  
  
  pN3b
  
  pN3c
Metastases in 10 or more axillary (armpit) lymph nodes;
or in infraclavicular (below the clavicle) (Level III axillary) lymph nodes;
or positive ipsilateral (on the same side) internal mammary lymph nodes by imaging in the presence of one or more positive Level I, II axillary lymph nodes;
or in more than three axillary lymph nodes and micrometastases or macrometastases by sentinel lymph node biopsy in clinically negative ipsilateral internal mammary lymph nodes;
or in ipsilateral supraclavicular (above the clavicle) lymph nodes.
Metastases in 10 or more axillary (armpit) lymph nodes (at least one tumor deposit larger than 2.0 mm);
or metastases to the infraclavicular (below the clavicle) (Level III axillary) lymph nodes.
pN1a or pN2a in the presence of cN2b (positive internal mammary nodes by imaging);
or pN2a in the presence of pN1b.
Metastases in ipsilateral (on the same side) supraclavicular (above the clavicle) lymph nodes.
Note: (sn) and (f) suffixes should be added to the N category to denote confirmation of metastasis by sentinel node biopsy or FNA/core needle biopsy respectively, with NO further resection of nodes.
Metastasis (M)
M0 No clinical or radiographic evidence of distant metastases.
  cM0(i+) No clinical or radiographic evidence of distant metastases in the presence of tumor cells or deposits no larger than 0.2 mm detected microscopically or by molecular techniques in circulating blood, bone marrow, or other nonregional nodal tissue in a patient without symptoms or signs of metastases.
cM1 Distant metastases detected by clinical and radiographic means.
pM1 Any histologically proven metastases in distant organs; or if in non-regional nodes, metastases greater than 0.2 mm.

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer Science+Business Media.

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