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Breast cancer

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Stages of breast cancer

Staging is a way of describing or classifying a cancer based on the extent of cancer in the body. The most common staging system for breast cancer is the TNM system. The International Union Against Cancer (UICC) uses theTNM system to describe the extent of many solid tumour cancers.

TNM

TNM stands for tumour, nodes, metastasis. TNM staging describes:

  • the size of the primary tumour
  • the number and location of any regional lymph nodes that have cancer cells in them
  • whether the cancer has spread or metastasized to a different part of the body

Primary tumour (T)

TX

Primary tumour cannot be assessed

T0

No evidence of primary tumour

Tis

Carcinoma in situ (non-invasive cancer) – Cancer cells are confined to the area where they first formed.

  • ductal carcinoma in situ (DCIS)
  • lobular carcinoma in situ (LCIS)
  • Paget disease of the nipple with no underlying breast tumour
    • Paget disease of the nipple associated with a tumour is classified according to the size of the tumour.

T1

An invasive tumour that is 2 cm or less in diameter.

T1mic

Microinvasion of 0.1 cm or less – Cancer cells have spread beyond the basement membrane (the boundary that separates one group of normal cells from the next) into nearby tissue.

T1a

Tumour is larger than 0.1 cm, but not more than 0.5 cm.

T1b

Tumour is larger than 0.5 cm, but not more than 1 cm.

T1c

Tumour is larger than 1 cm, but not more than 2 cm.

T2

Invasive tumour that is larger than 2 cm, but not more than 5 cm.

T3

Invasive tumour that is larger than 5 cm.

T4

Tumour is any size and has spread to the chest wall or skin. The chest wall includes the ribs and some of the muscles in the chest.

T4a

The tumour has spread to the chest wall, but not to the pectoral muscle.

T4b

There are signs of the tumour, including swelling (edema), peau d’orange or sores (ulcers) on the skin of the breast or skin nodules in the breast.

T4c

Includes both T4a and T4b

T4d

Lymph node staging

Regional lymph nodes are lymph nodes around the breast on the same side of the body as the breast cancer (ipsilateral lymph nodes). Clinical staging of lymph nodes is based on physical (clinical) examination or imaging studies. If cancer is detected in the lymph nodes using these methods, it is called clinically apparent.

Pathological staging involves surgically removing some of the lymph nodes and examining them under a microscope to see if they contain cancer. A small “p” may be used to designate the pathological classification of regional lymph nodes (for example, pN1a, pN2b, pN3c).

Regional lymph nodes (N)

NX

Regional lymph nodes cannot be assessed

N0

No regional lymph node metastasis (lymph node–negative breast cancer)

N1

Regional lymph node metastasis (lymph node–positive breast cancer) – Cancer has spread to lymph nodes in the armpit (axillary lymph nodes), the lymph nodes around the breastbone (internal mammary lymph nodes) or both.

Clinical

N1 – Cancer is in axillary lymph node(s), which are movable.

Pathological

  • N1a – Cancer is in 1–3 axillary lymph nodes.
  • N1b – Cancer is in internal mammary lymph nodes.
  • N1c – Cancer is in 1–3 axillary lymph nodes and in internal mammary lymph nodes.

N2

Regional lymph node metastasis (lymph node–positive breast cancer) –

Cancer has spread to the axillary lymph nodes, internal mammary lymph nodes or both.

Clinical

  • N2a – Cancer is in axillary lymph nodes, which are fixed to one another (matted) or to other structures.
  • N2b – Cancer is clinically apparent in internal mammary lymph nodes, but not clinically apparent in axillary lymph nodes.

Pathological

  • N2a – Cancer is in 4–9 axillary lymph nodes.
  • N2b – Cancer is clinically apparent in internal mammary lymph nodes, but has not spread to axillary lymph nodes.

N3

Regional lymph node metastasis (lymph node–positive breast cancer) – Cancer has spread to one of the following:

  • axillary lymph nodes (with or without spread to the internal mammary lymph nodes)
  • lymph nodes below the collarbone (infraclavicular lymph nodes)
  • lymph nodes above the collarbone (supraclavicular lymph nodes)

Clinical

  • N3a – Cancer is in infraclavicular lymph node(s).
  • N3b – Cancer is in internal mammary lymph node(s) and axillary lymph nodes(s).
  • N3c – Cancer is in supraclavicular lymph node(s).

Pathological

  • N3a – Cancer is in 10 or more axillary lymph nodes or in infraclavicular lymph node(s).
  • N3b – Cancer is clinically apparent in internal mammary lymph nodes and 1 or more axillary lymph nodes, or cancer is in more than 3 axillary lymph nodes and in internal mammary nodes detected by lymph node biopsy.
  • N3c – Cancer is in supraclavicular lymph nodes.

Distant metastasis (M)

M0

No distant metastasis

M1

Distant metastasis – Includes lymph node metastasis other than regional lymph nodes, such as metastasis in lymph nodes in the neck (cervical lymph nodes) or internal mammary lymph nodes on the side opposite the breast cancer (contralateral lymph nodes).

Stage grouping for breast cancer

The UICC further groups the TNM data into the stages listed in the table below.

UICC staging – breast cancer
UICCTNMExplanation

stage 0

Tis

N0

M0

In situ cancer – Cancer is confined to the ducts, lobules or nipple and has not spread to nearby breast tissue.

Cancer has not spread to the lymph nodes.

Cancer has not spread to distant sites

stage I

T1

N0

M0

The tumour is 2 cm or less in diameter.

Cancer has not spread to the lymph nodes.

Cancer has not spread to distant sites.

stage IIA

T0

N1

M0

No tumour is found in the breast.

Cancer is found in 1–3 axillary lymph nodes.

Cancer has not spread to distant sites.

T1

N1

M0

The tumour is 2 cm or less in diameter.

Cancer has spread to 1–3 axillary lymph nodes, internal mammary lymph nodes or both.

Cancer has not spread to distant sites.

T2

N0

M0

The tumour is larger than 2 cm, but not more than 5 cm in diameter.

Cancer has not spread to the lymph nodes.

Cancer has not spread to distant sites.

stage IIB

T2

N1

M0

The tumour is larger than 2 cm, but not more than 5 cm in diameter.

Cancer has spread to 1–3 axillary lymph nodes, internal mammary lymph nodes or both.

Cancer has not spread to distant sites

T3

N0

M0

The tumour is more than 5 cm in diameter.

Cancer has not spread to the lymph nodes.

Cancer has not spread to distant sites.

stage IIIA

T0

N2

M0

No tumour is found in the breast

Cancer is found in 4–9 axillary lymph nodes or in internal mammary lymph nodes.

Cancer has not spread to distant sites.

T1

N2

M0

The tumour is 2 cm or less in diameter.

Cancer has spread to 4–9 axillary lymph nodes or to internal mammary lymph nodes.

Cancer has not spread to distant sites.

T2

N2

M0

The tumour is larger than 2 cm, but not more than 5 cm in diameter.

Cancer has spread to 4–9 axillary lymph nodes or to internal mammary lymph nodes.

Cancer has not spread to distant sites.

T3

N1, N2

M0

The tumour is more than 5 cm in diameter.

Cancer has spread to 1–9 axillary nodes or to internal mammary lymph nodes.

Cancer has not spread to distant sites.

stage IIIB

T4

N0, N1, N2

M0

The tumour has spread to the chest wall or skin.

One of the following applies:

  • Cancer has not spread to any lymph nodes.
  • Cancer has spread to 1–9 axillary lymph nodes.
  • Cancer may or may not have spread to internal mammary lymph nodes.

Cancer has not spread to distant sites.

stage IIIC

any T

N3

M0

The tumour is any size.

One of the following applies:

  • Cancer has spread to 10 or more axillary lymph nodes.
  • Cancer has spread to 1 or more infraclavicular or supraclavicular lymph nodes.
  • Cancer has spread to more than 3 axillary lymph nodes and to internal mammary lymph nodes.

Cancer has not spread to distant sites.

T4d

Inflammatory breast cancer is classified as stage III (IIIB or IIIC), unless it has spread to distant sites or lymph nodes far from the breast, in which case it is stage IV.

stage IV

any T

any N

M1

The tumour is any size.

Any degree of lymph node involvement.

Cancer has spread to distant sites, such as the bone, liver, lung, brain or lymph nodes far from the breast.

Note: Stage III breast cancer may also be called locally advanced breast cancer.

Recurrent breast cancer

Recurrent breast cancer means that the cancer has come back after it has been treated. It may recur in the same location as the original cancer (local recurrence), such as in the breast itself, the skin or the chest wall. It may also recur in another part of the body (metastatic breast cancer).

Stories

Lusomé Founder and CEO Lara Smith Seeing my sister Erin – a young mother – struggle with the emotional blow and then the physical toll of cancer treatment made me want to do something to help women feel confident.

Read Lara's story

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