Understanding Your Breast Cancer Stage

Knowing the stage of your breast cancer helps your medical team determine how big the cancer is and if it has spread. This helps them guide your therapy and provide reliable prognostic information.

In general, staging is done following your surgery, either after lumpectomy or mastectomy. It usually includes evaluation of the lymph nodes in your armpit (axillary lymph nodes), and possibly other radiology tests and blood work.

All breast cancers are staged using a system defined by the American Joint Committee on Cancer based on the “TNM system.” TNM refers to tumor size (T), number of lymph nodes involved (N), and whether your cancer has metastasized (or spread) to other parts of your body (M).  The newest edition was released in late 2009 and took effect Jan 1, 2010.

The following is an overview of the updated TNM staging system for breast cancer. Interestingly, due to the increased use of neoadjuvant chemotherapy, recommendations are now also given for staging of patients who have undergone such therapy. I have tried to highlight some of the more major changes in the 2009 edition, but there are many smaller changes that are beyond the scope of this article. If interested, a very detailed explanation of the changes to the staging guidelines is available here.

T:  The size of the cancer.

Tx:  The primary tumor size cannot be assessed

T0:  No cancer is present.

Tis:  Non-invasive cancer, also known as carcinoma in situ, is present (DCIS or LCIS or Paget’s disease alone).

T1:  Invasive cancer measuring 2 centimeters or smaller is present. This is further sub-divided into four groups:

Tmic:  microinvasive cancer, meaning the invasive cancer is 1 millimeter or smaller.

T1a:  the invasive cancer measures greater than 1 millimeter but not greater than 5 millimeters.

T1b:  the invasive cancer measures greater than 5 millimeters but not greater than 1 centimeter.

T1c:  the invasive cancer measures greater than 1 centimeter but not greater than 2 centimeters.

T2:  Invasive cancer is present, measuring greater than 2 centimeters but not greater than 5 centimeters.

T3:  Invasive cancer is present, measuring greater than 5 centimeters.

T4:  Invasive cancer is invading the chest wall or skin; also includes inflammatory cancer. In the 2009 edition, the diagnosis of inflammatory carcinoma is more clearly defined and the finding of carcinoma merely invading the dermis of the skin alone was not felt to represent T4 disease.

N:  The number of lymph nodes involved by cancer.

Nx:  Lymph nodes cannot be assessed.

N0:  No cancer found in lymph nodes.  In 2002 and again in the 2009 edition, an addition was made for the diagnosis of isolated tumor cells (ITCs) but changes to the definition were added in 2009 as well as an addition for findings by molecular studies:

N0(i+):  Cells found in the lymph node measuring 0.2 millimeters or less, found either on routine pathology or using immunohistochemistry. In 2009, the following addition was made: if more than 200 cancer cells are found in a particular node, that node should be classified as a micrometastasis (N1mic) not isolated tumor cells.

N0(mol+):  Positive molecular findings using RT-PCR but negative nodes histologically or by immunohistochemistry.

N1:  Cancer is present in 1-3 lymph nodes in the armpit area (also known as axillary lymph nodes).

N1mic:  The cancer present in the lymph node measures greater than 0.2 millimeters but not greater than 2 millimeters.  This is also known as a micrometastasis.

N2:  Cancer is present in 4-9 axillary lymph nodes.

N3:  Cancer is present in 10 or more axillary lymph nodes.

M:  The presence or absence of distant metastases.

M0:  No distant metastases are present.  In the 2009 edition, a category of M0(i+) was defined for patients without evidence of distant metastases by clinical or imaging studies, but molecular studies identify foci of carcinoma in blood, bone marrow, or other body site which are no larger than 0.2 mm.

M1:  Distant metastases are present.

Once you know your T, N, and M status, you can determine your breast cancer stage as follows based upon the new guidelines:

Stage 0:  Tis, N0, M0

Stage IA:  T1, N0, M0

Stage IB:  T0/T1 with N1mic, M0

Stage IIA:  T0/T1 with N1, M0  or T2, N0, M0

Stage IIB:  T2, N1, M0 or T3, N0, M0

Stage IIIA:  T0/T1/T2 with N2, M0 or T3 with N1 or N2 and M0

Stage IIIB:  T4 with N0/N1/N2 and M0

Stage IIIC:  Any T with N3 and M0

Stage IV:  Any T with any N with M1

© 2010 Seattle Breast Pathology Consultants, LLC. All rights reserved.

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