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Understand Breast Cancer Staging: TNM Classification of Breast Cancer


Staging helps to determine the disease prognosis and to select an appropriate treatment strategy.

TNM is the most commonly used staging system for breast cancer. It uses mainly 3 parameters: “T” stands for “Tumor”; “N” for “Lymph Nodes”; and “M” for “Metastasis”.

Numbers and/or letters after T (0, is, 1, 2, 3, and 4), N (0, 1mi, 1, 2, and 3), and M (0 and 1) provide more details about each of these parameters. Once T, N, and M are determined, it is used to assign an overall stage (from 0 to IV).

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Breast Cancer - T Staging
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Breast Cancer - N Staging
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Breast Cancer - M Staging
STAGE TNM DESCRIPTION
0 Tis N0 M0 Pre-cancerous changes or carcinoma in situ (CIS). No spread to nearby lymph nodes or distant body parts.
IA T1 N0 M0 Tumor size is 2 cm or less. No spread to nearby lymph nodes or distant body parts.
IB T0-1 N1mi M0 CIS or tumor </=2 cm in size with spread to the lymph nodes under the arm >0.2 mm, but </=2 mm in size (micrometastases). No spread to distant body parts.
IIA T0-1 N1 M0 CIS or tumor </=2 cm in size with cancer spread to 1-3 axillary (underarm) lymph nodes or tiny cancer deposits in internal mammary lymph node(s) (those near the breastbone) on sentinel lymph node biopsy. No spread to distant body parts.
OR
T2 N0 M0 Tumor size >2 cm, but </=5 cm. No spread to nearby lymph nodes or distant body parts.
IIB T2 N1 M0 Tumor size >2 cm, but </=5 cm with cancer spread to 1-3 axillary lymph nodes or tiny cancer deposits in internal mammary lymph node(s) on sentinel lymph node biopsy. No spread to distant body parts.
OR
T3 N0 M0 Tumor size >5 cm. No spread to nearby lymph nodes or distant body parts.
IIIA T0-2 N2 M0 CIS or tumor </=5 cm in size with cancer spread to 4-9 axillary lymph nodes or enlargement of internal mammary lymph node(s). No spread to distant body parts.
OR
T3 N1-2 M0 Tumor size >5 cm with cancer spread to 1-9 axillary lymph nodes or spread to internal mammary lymph node(s). No spread to distant body parts.
IIIB T4 N0-2 M0 Tumor of any size with direct extension to the chest wall or skin or inflammatory breast cancer. No spread to nearby lymph nodes or cancer spread to 1-9 axillary lymph nodes or spread to internal mammary lymph node(s). No spread to distant body parts.
IIIC AnyT N3 M0 Tumor of any size with spread to

>/=10 axillary lymph nodes (>/=1 area >2 mm), or cancer spread to the infraclavicular (those under the collarbone) lymph nodes (>/=1 area >2 mm) [N3a],

or cancer spread to >/=1 axillary lymph nodes (>/=1 area >2 mm) with internal mammary lymph node(s) enlargement, or cancer spread to >/=4 axillary lymph nodes (>/=1 area >2 mm) with micrometastasis in internal mammary lymph node(s)[N3b], or

cancer spread to the supraclavicular (those above the collarbone) lymph nodes (>/=1 area >2 mm)[N3c].

No spread to distant body parts.
IV AnyT AnyN M1 Tumor of any size with no or any extent of spread to nearby lymph nodes. Cancer spread to distant organs like bones, lungs, liver, brain, etc.

In addition to staging, estrogen receptor (ER), progesterone receptor (PR), HER2/neu (HER2) status, and grade of the cancer is evaluated on the surgical specimen to assess the prognosis of the disease, and planning the treatment.

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Watch the video below to better understand the ANATOMY AND STAGING OF BREAST CANCER AND AXILLARY LYMPH NODES.

After we have staged the disease, we broadly divide the breast cancer into a particular stage group, ie, whether it is a localised, locally advanced or metastatic breast cancer, as shown in the infographic below.

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Breast Cancer - Stage Grouping

Watch the video below to better understand the STAGE GROUPING of breast cancer.

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