TNM Staging Breast Cancer


The breasts are paired, hemispherical-shaped, glandular organs of variable size on the chest of a woman (between the 2nd and 6th ribs and anterior to pectoral muscles). They are mostly made up of adipose (fatty) tissue and connective (fibrous) tissue that surrounds and support about 12 to 20 lobes. The nipple is surrounded by the dark skin called the areola.

Epithelial breast carcinoma or adenocarcinoma (affecting epithelial cells of the glandular tissue within breast) is the most commonly encountered (more than 95% of all cases) type of breast cancer. Breast adenocarcinoma includes ductal carcinoma in situ, invasive ductal carcinoma, and invasive lobular carcinoma.

Breast Cancer Hormone Receptors: Normal breast cells and some breast cancer cells have specialized proteins on/in their surface called hormone receptors. Hormones – estrogen and progesterone can bind to these receptors (estrogen receptor [ER] and progesterone receptor [PR], respectively) and promote the growth of these cells.

Some breast cancer cells have another growth-promoting protein on/in their surface known as the human epidermal growth factor receptor 2 (HER2/neu or HER2). Certain breast cancer cells do not have any of the above receptors, that is, negative for ER, PR, and HER2. These are called triple-negative breast cancer.

TNM Staging of Breast Cancer – Clinical

Clinical TNM Staging for breast cancer is done by physical examination of the patient and loboratory and radiology investigations (discussed below).

T Staging

It is called as T1 when the tumor size is less than or equal to 2 cm. T1 - Tumor is less than or equal to 2 cm T2 when the tumor is 2 cm to 5 cm. T2 tumor is 2 cm to 5 cm And T3 when the tumor is more than 5 cm. T3 tumor is more than 5 cm To understand T4 disease, first we have to know the structures. Deep to the breast there is pectoralls fascia and pectoralls major muscle.

pectoralls fascia and pectoralls major muscle And here lies the pectoralis minor muscle.

pectoralis minor muscle Other structures in the chest wall include ribs and intercostal muscles. If we look from the front of the chest, this is the pectoralis major muscle.

pectoralis major muscle And this is the serratus anterior muscle.

serratus anterior muscle T4a disease is when the tumor infiltrates the chest wall, not including only pectoralis muscle adhesion or invasion. And here, the tumor infiltrates into the serratus anterior muscle.

T4a - Involvement of serratus anterior T4b disease is involvement of skin by the tumor.

T4b - involvement of skin It can present as skin ulceration or as satellite tumor nodules.

T4b - Skin ulceration   t4b - satellite tumor nodules   Or as edema of skin looking like an orange peel known as peau de orange.

t4b - peau de orange All the skin changes should occupy less than one-third of the surface area of breast to be called as T4b. Infiltration of tumor into both, chest wall and skin, i.e., T4a and T4b both, is called T4c.

And when the breast cancer progresses very rapidly to cause diffuse erythema and edema of skin breast, involving more than one-third of the skin, then it is called as inflammatory breast cancer.

Breast Cancer T Staging

N Staging

Now, we move on to the N-staging. To understand the N staging, first you have to know the local structures in that area.

In this figure, you can see the humerus, clavicle and sternum bone. humerus, clavicle and sternum bone This is the pectoralls minor muscle.

pectoralls minor muscle These nodular structures in the anterior axillary fold, are called as anterior group of lymph nodes. anterior axillary group of lymph nodes And along the head of the humerus are lateral group of lymph nodes. All these three groups, lateral to pectoralis minor muscle, are level 1 lymph nodes.

These present behind the pectoralls minor muscle are central, or level 2 lymph nodes. level 2 or central group of lymph nodes And these present medial to pectoralls minor muscle, are apical or level 3 lymph nodes.

And these, along the sternum are called as internal mammary lymph nodes.

internal mammary lymph nodes For clinical N-staging, we have to palpate level 1 and 2 lymph nodes in axilla. If they are not palpable, it is NO. If palpable, and freely mobile, it is N1. If level 1 or level 2 lymph nodes are palpable, but they are fixed or matted, it is called as N2a. If only internal mammary lymph nodes are seen in CT scan without any level 1 or level 2 nodes, the it is called as N2b. N2b stage - only internal mammary nodes involved If infraclavicular lymph nodes are involved, it is called as N3a.

N3a - infraclavicular lymph nodes involvement If internal mammary and axillary lymph nodes both are involved that is N2a and N2b, then it is N3b.

N3b - Involvement of both internal mammary and axillary lymph nodes Involvement of supraclavicular lymph nodes are called as N3c.

N3c - supraclavicular lymph nodes involved

Breast Cancer N Staging

M Staging

Now, let’s move ahead. Next comes the M-staging If the disease has spread to the distance organ it is called as M1 otherwise it is M0. This figure shows spread to both lungs in the form or multiple metastatic nodules.

metastasis to lungs And here, metastasis to the pleura has resulted in fluid collection, called as pleural effusion. pleural effusion This figure shows spread to the liver in form or multiple nodular deposits. spread to liver And here, the cancer is spread to the adrenal gland. spread to adrenal gland

Similarly, the spread may occur to brain, bones or other part of the body.

Breast cancer M Staging

TNM Staging of Breast Cancer – Pathological

Pathological TNM Staging for breast cancer is done on surgical specimen of breast and regional lymph nodes.

T Staging

Tis – Pre-cancerous changes or carcinoma in situ (CIS). No spread to nearby lymph nodes or distant body parts.

T1 – Tumor size is 2 cm or less. No spread to nearby lymph nodes or distant body parts.

T2 – Tumor size >2 cm, but </=5 cm. No spread to nearby lymph nodes or distant body parts.

T3 – Tumor size >5 cm. No spread to nearby lymph nodes or distant body parts.

T4 – Tumor of any size with direct extension to the chest wall or skin or inflammatory breast cancer.

N Staging

N1 – Cancer spread to 1-3 axillary lymph nodes or tiny cancer deposits in internal mammary lymph node(s) on sentinel lymph node biopsy.

N2 – Cancer spread to 4-9 axillary lymph nodes or enlargement of internal mammary lymph node(s).

N3 – >/=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],

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].

M Staging

M0 – No spread of the disease to distant body parts.

M1 – Cancer spread to distant organs like bones, lungs, liver, brain, etc.

Breast Cancer Staging Chart

Based on the TNM Staging discussed above, breast cancer can be classified into 4 stages as discussed below.

Stage TNM
0 Tis N0 M0
IA T1 N0 M0
IB T0-1 N1mi M0
IIA T0-1 N1 M0
  T2 N0 M0
IIB T2 N1 M0
  T3 N0 M0
IIIA T0-2 N2 M0
  T3 N1-2 M0
IIIB T4 N0-2 M0
IV AnyT AnyN M1

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.

Stage Grouping – Localised, Locally Advanced and Metastatic Breast Cancer

To make things easier, we stage the breast cancer into stage groups. It can broadly be divided into localized, locally advanced or metastatic disease.

Localised disease includes cases up to T2 N1 M0 and T3 N0 M0. Starting from T3 N1 M0 and onwards all N2 and N3 and T4 cases are included under locally advanced disease. Metastasis to other sites, as we have discussed previously is called M1 disease. localised, locally advanced and metastatic breast cancer

Survival Rate/ Life Expectancy based on Staging

Localised disease

  • Cancer is limited to the breast.
  • 5 year survival 99%.

Regional disease

  • Cancer has spread to nearby structures or lymph nodes
  • 5 year survival 86%.

Distant spread

  • Cancer has spread to distant body parts.
  • 5 year survival 27%.

Breast Cancer Staging Investigations

breast cancer staging investigations


It uses low dose X-rays to examine the breasts. In this test, a special machine has used that consist of two plates to compress and flatten the breast to be examined. Thereafter, an X-ray image of the breast is taken. This test can provide information about the cancerous changes within the breast tissue which generally appears as a lump/mass, microcalcifications, or other changes. Any abnormality observed during this test warrants detailed investigations to establish the diagnosis of breast cancer. Mammograms are not very sensitive in case of dense breast tissue. Mammography imaging of the breast is reported as a score called BIRADS score.

  • BIRADS 1 means absolutely normal breast, with 0% chances of malignancy.
  • BIRADS 2 means the presence of benign findings, with 0% chances of malignancy.
  • BIRADS 3 means the presence of findings that are probably benign, with less than 2% chances of malignancy. Needle testing of breast is not required in BIRADS 1, 2 or 3.
  • BIRADS 4 means suspicious for malignancy, with 2-95% chances of malignancy. Needle testing should be considered in this.
  • BIRADS 5 means highly suggestive of malignancy, with more than 95% chances of malignancy. Needle testing should be done in this.

Needle testing of breast may be done by FNAC or biopsy, but biopsy is preferred as it is more accurate, and provides sufficient tissue for ER, PR and HER-2 testing.

Breast ultrasound

breast ultrasound This test can distinguish between fluid-filled cysts (mostly benign) and solid tumor masses. This technique can also be used to guide a needle to collect biopsy samples.

Breast Biopsy

  • Biopsy sample is generally collected from the suspected areas observed during the mammography or the breast ultrasound.
  • Depending on the size and location of the suspicious area, a fine needle biopsy, a core needle biopsy, or a surgical biopsy technique is utilized.
  • Sometimes, a biopsy sample from lymph nodes under the arms may also be collected.
  • The collected biopsy samples are examined in a laboratory and can provide information about the type of cancer, grade of cancer, and the presence of specific defective genes or proteins in the cancer cells.
  • Breast cancer is classified into hormone receptor positive, Her-2 Neu positive or triple negative disease based on biopsy testing and it is very important as it determines the further treatment of the disease.

Systemic Imaging

So first we did a local imaging, when we had a suspicious mass in breast. Then we did a needle testing to confirm that it is cancer. Once the diagnosis of breast cancer is confirmed, we have to do the systemic imaging depending upon clinical presentation, to stage the disease, whether it is localised, locally advanced or metastatic. Any one or more of the following investigations may be required for staging work-up of the tumor-

  • Whole Body PET CT Scan
  • CT Scan
  • Bone Scan
  • X Ray Chest
  • USG Abdomen

Read more-

Risk factors for Breast Cancer

Treatment of Breast Cancer

Male Breast Cancer


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