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Breast Cancer Staging

Cancer patient with bandana
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Cancer staging

Breast cancer staging pictureStaging is a method of categorising cancers based on their size, invasiveness and if they have spread to other sites in the body. This information can be used to quantify the prognosis (likely outcome), to determine the most suitable treatments for a particular individual, and to help compare treatment groups in clinical trials.


What is the TNM staging system?

The staging system most widely used by doctors for breast cancer is the TNM system. This system groups cancers into stages based on three primary aspects:

  • Tumour (T): The extent of the primary tumour. For example, the size of the tumour, its type and/or invasiveness (direct spread into nearby structures);
  • Nodes (N): The number and location of lymph nodes (collections of cells that act as a filter for the immune system) involved; and
  • Metastases (M): If there are any distant metastases (spread of the tumour through the bloodstream to distant sites, for example breast cancer spreading through the blood to create a new tumour in a bone).

The TNM system is maintained and updated regularly by two bodies, the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC). The most recent revision is the seventh edition, and applies to all cancers diagnosed on or after 1 January 2010.

Once information about the primary tumour (T), lymph node involvement (N) and distant metastases (M) is gathered through clinical, radiological and pathological examination (see below), the tumour can be given a grade based on the individual components T, N and M.


Tumour

The first section of the TNM staging system refers to the primary tumour. The designation (in bold) is based on the greatest diameter of the primary tumour, its invasiveness and also the type of tumour.

TXAssessment of the primary tumour cannot be made.
T0No evidence of the primary tumour.
T1Tumour ≤ 20 mm in greatest dimension. This can be further classified according to size.
T2Tumour > 20 mm but ≤ 50 mm in greatest dimension.
T3Tumour > 50 mm in greatest dimension
T4Any size tumour that demonstrates direct extension (invasion) into the chest wall and/or to the skin. This can be further classified.
Tis Carcinoma in situ.
Tis (DCIS) Ductal carcinoma in situ (where the cancer cells resemble that of the breast ducts)
 Tis (LCIS)Lobular carcinoma in situ (where the cancer cells resemble that of the breast glands or lobules).
Tis (Paget’s) Paget’s disease of the nipple (an uncommon breast cancer forming in or around the nipple) NOT associated with invasive carcinoma and/or carcinoma in situ (DCIS and/or LCIS) in the underlying breast tissue.

 

Breast anatomy pictureFor more information on the breast, see Anatomy of the Breast.


Nodes

The second component of the TNM staging system refers to the involvement of lymph nodes. Designations are again in bold.

NXAssessment of regional lymph nodes cannot be made (e.g. previously removed).
N0No regional lymph node involvement.
N1Involvement of lymph nodes in the axilla (arm pit) on the same side as the primary tumour. The lymph nodes affected are still moveable and not anchored to surrounding tissue.
N2Involvement of lymph nodes in the axilla on the same side as the primary cancer that are fixed to surrounding structures OR where internal mammary nodes on the same side as the primary tumour are involved without evidence of lymph nodes in the axilla being affected.
N3Involvement of lymph nodes that lie above or below the clavicle bone (collar bone) OR those affecting both mammary lymph nodes and lymph nodes in the axilla on the same side as the primary tumour.


Where tissue has been removed by surgery and investigated by a pathologist, further classifications can be given. This is denoted by the prefix p.


Metastases

The final component of the TNM staging system is dependent on whether there is any evidence for metastases to distant sites.

M0No clinical or radiographic evidence of distant metastases.
cM0(i+)No clinical or radiographic evidence of distant metastases, but deposits of molecularly or microscopically detected tumour cells in circulating blood, bone marrow, or other non-regional nodal tissue that are no larger than 0.2 mm in a patient without symptoms or signs of metastases.
M1Distant detectable metastases as determined by classic clinical and radiographical means and/or histologically proven to be larger than 0.2 mm.


Final grouping

Once information is gathered pertaining to T, N, and M, this can be used to determine the stage as outlined below:

Stage 0Tis N0 M0
Stage IAT1 N0 M0
Stage IBT0 N1 M0
T1 N1 M0
Stage IIAT0 N1 M0
T1 N1 M0
T2 N0 M0
Stage IIBT2 N1 M0
T3 N0 M0
Stage IIIAT0 N2 M0
T1 N2 M0
T2 N2 M0
T3 N1 M0
T3 N2 M0
Stage IIIBT4 N0 M0
T4 N1 M0
T4 N2 M0
Stage IIICAny T N3 M0
Stage IVAny T Any N M1

From this we can see that any cancer that has given rise to distant metastases is stage IV, and any tumour less than 20 mm in maximal diameter without lymph node involvement or distant metastases is stage IA.


Modalities used to stage breast cancer

Breast cancer staging pictureStaging of a breast cancer involves clinical, radiological and pathological examinations.


Clinical examination

Clinical examination includes history taking, physical examination and laboratory investigations.

History taking should be comprehensive and include:

Examination includes:

  • Palpation of both breasts (the breasts are observed and felt in a systemised way to detect any breast lumps); and
  • Palpation of local regional lymph nodes, for example those in the arm pit or surrounding the clavicle (collar bone).

Investigations should include:

  • Full blood picture: A blood test that reports the number of red and white blood cells;
  • Liver function test: To assess if liver function is affected by cancer spreading to the liver;
  • Renal function tests: To determine the satisfactory function of the kidneys;
  • Alkaline phosphatase levels: If high, it may indicate the possibility of cancer spreading to bone; and
  • Calcium levels: If high, it may indicate the possibility of cancer spreading to bone.

If menopausal status is uncertain, it should be clarified, as it can affect which treatments are offered.


Radiological examination

Radiological investigation most commonly involves mammography of both breasts and/or ultrasound of the breast.

Magnetic resonance imaging (MRI) is not routinely used but can be useful in certain situations, including for younger women with dense breast tissue, those with familial breast cancer, those in which secondary spread to lymph nodes is observed but there is no identifiable primary tumour, or if the doctor suspects multiple tumour sites.

Other imaging to exclude metastases may be performed, including:

  • Chest x-ray;
  • Abdominal ultrasound; and/or
  • Bone scan.

Patients with early stage breast cancer N0 do not benefit from extensive radiological investigations.


Pathological examination

Breast cancer staging picturePathological investigations include samples from fine needle aspiration (where a needle is introduced to collect a sample), core needle biopsy (a larger needle is used for a more complete sample) or complete surgical specimens (those removed by surgery).

The information gained from fine needle aspiration and core needle biopsy includes the type and grade of the cancer as well as determination of oestrogen receptor, progesterone receptor and HER2 receptor status, which can affect what treatments are offered.

Evaluation of surgical specimens usually includes:

  • The number, location and maximum diameter of all tumours resected (removed);
  • Evaluation of the resection margin (i.e. how much normal tissue has been removed along with the tumour);
  • Presence of invasion into blood vessels or lymphatic system;
  • Determination of oestrogen, progesterone and HER2 receptor status;
  • The total number of lymph nodes removed, and the number of these that are positive; and
  • For tumour-positive lymph nodes, the extent of the metastases should be described, including isolated tumour cells, micrometastases (0.2–2 mm), or macrometastases.


Benefits and limitations of tumour staging

The benefit of a staging system is that it is a structured method of describing the anatomical extent of a cancer, which can then be used to provide information about the prognosis, direct treatment, assess the chance of successful treatment outcomes, or help compare treatment groups in clinical trials.

However, with advances in molecular biological techniques, our understanding of breast cancer is no longer one of a single disease entity. There are many different subtypes of breast cancers that may behave differently to each other. While the latest edition of the TNM staging system has tried to incorporate differences in biology, some cancers may show little correlation between the tumour stage and the clinical outcome.


Conclusion

The main reason for staging cancers is to provide a means to quantify prognosis and provide appropriate treatment strategies for optimal patient outcomes. To illustrate this, tumours greater than 4 cm in diameter or with many sites would not be candidates for breast conserving therapy, an alternative that offers more cosmetic results than does mastectomy. Post-operative radiotherapy would be recommended for most women undergoing breast conserving therapy; for those undergoing mastectomy, it would only be recommended for patients with T3–T4 tumours ,or those where the cancer has spread to the lymph nodes in the axilla or beyond. Patients with oestrogen receptor positive breast cancers can be treated with tamoxifen (sold as Tamoxen or Genox); those with cancers that lack the hormone receptors should not receive endocrine therapy. Having a widely accepted and used staging system gives clinicians the means to describe the anatomical extent and biology of breast cancers, and so direct the most appropriate therapies for women with breast cancer.

More information

Breast cancer
For more information on breast cancer, types of breast cancer and its investigations and treatments, as well as some useful videos, see
Breast Cancer.

Kindly written by:

Dr Allison Johns
BSc (Biomed/Mol Biol) Hons, MBBS
Doctor, Royal Perth Hospital, and Editorial Advisory Board member of the Virtual Medical Centre

References

  1. Edge SB, Compton CC. The American Joint Committee on Cancer: The 7th edition of the AJCC cancer staging manual and the future of TNM. Ann Surg Oncol. 2010;17(6):1471-4. [Abstract ‌‌| Full text]‌
  2. Breast cancer staging [online]. Chicago, IL: American Joint Committee on Cancer; 2009 [cited 25 May 2010]. Available from: URL link
  3. Aebi S, Davidson T, Gruber G, Castiglione M. Primary breast cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2010;21(Suppl 5):v9-14. [Abstract | Full text]
  4. Park YH, Lee SJ, Cho EY, et al. Clinical relevance of TNM staging system according to breast cancer subtypes. Ann Oncol. 2011;22(7):1554-60. [Abstract]
  5. Clinical practice guidelines in oncology: Breast cancer [online]. Fort Washington, PA: National Comprehensive Cancer Network; 2011 [cited 17 April 2011]. Available from: URL link
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Dates

Posted On: 18 July, 2011
Modified On: 13 October, 2014


Created by: myVMC