Breast cancer is one of the most prevalent cancers among Indian women. As per a 2019 report published in NCBI, breast cancer constitutes more than 30 per cent of all cancers in females.

The survival rate largely depends on early diagnoses and the right treatment.

Breast tumour size is an important factor in determining breast cancer stage but not the only one. Other factors like the location of the tumour, how much it has spread, hormone receptor status also play a significant role in deciding the stage of breast cancer.

Doctors use various tests and examinations to evaluate the specific characteristics of a person’s breast cancer while determining breast cancer stages.

The TNM Staging System

The diagnostics tests and scans of the person help the doctors in tumour staging.  The TNM staging system is a commonly used tool to describe the stage.

• T (Tumour) – How large is the size of the primary tumour?
• N (Node) – Has the cancer spread to the nearby lymph nodes?
• M (Metastasis) – Is the cancer metastatic, i.e., has it spread to distant parts of the body like liver, lungs, bones, or brain?

Combined results are used to determine the stage of cancer for each person.

1) T – Measuring Breast Tumour Size and Staging

Tumour size is generally measured in millimetres (mm) or centimetres (cm). A number suffixed with T tells you the main tumour’s size. Higher the number, larger is the tumour and its spread.

The American Cancer Society uses this particular system for tumour staging:

TX – The primary tumour cannot be evaluated

T0 – No evidence of cancer in the breast

T1 – The tumour detected is less than 20 mm in size. It further has four sub-stages categorized as per the size of tumour:

• T1mi – less than 1 mm
• T1a – between 1 mm to 5 mm
• T1b – between 5 mm to 10 mm
• T1c – between 10 mm to 20 mm

T2 – When the tumour is larger than 20 mm but smaller than 50 mm

T3 – When the tumour is larger than 50 mm

T4 – The tumour has grown into the chest wall and/or skin. It also includes inflammatory breast cancer.

2) N – Lymph Node Status and Staging

The N value of the TNM staging system assesses whether cancer has spread to the nearby lymph nodes. The doctor generally takes the sample from the armpit area called the axillary lymph nodes and graded through the following:

• NX – Unable to evaluate lymph node status
• N0 – No cancer detected in the nearby lymph nodes
• N1 – The cancer has spread to 1 to 3 lymph nodes
• N2 – It has spread to 4 to 9 lymph nodes
• N3 – It has spread to 10 or more lymph nodes

3) M – Metastasis and Staging

When cancer cells have spread to distant organs or tissues of the body, it is metastatic breast cancer. The most common metastatic areas are the liver, bones, and lungs. The assessment is as follows:

MX – Unable to evaluate the distant spread

M0 – No evidence found for cancer spreading to distant parts

M1 – Cancer has spread to distant parts

Other Factors Affecting Breast Cancer Stages

Breast tumour size is one crucial determinant of the cancer stage along with lymph node and metastatic status.

However, some other deciding factors that doctors use to evaluate breast cancer staging are:

1) Hormone Receptor Status

Knowing the hormone receptor status is essential in tumour staging and also deciding an effective breast cancer treatment plan. For this, the doctors evaluate the breast cancer cells for specific proteins that are estrogen and progesterone receptors.

The cancer cells often attach themselves to these hormones and feed on them to grow.

• Estrogen receptors are identified as ER-positive (ER+) cancers.
• Progesterone receptors are identified as PR positive (PR+) cancers.
• If both the receptors are positive, then it is called hormone-positive (HR+) breast cancer.
• If both the receptors are negative, then it is called hormone negative (HR-) breast cancer.

Hormone therapy is generally the most effective treatment in such cases. It prevents estrogen and progesterone from attaching themselves to the receptors, thereby keeping cancer from growing and spreading.

2) HER2 Status

One of the newest determinants to be incorporated into breast cancer staging is HER2 status. HER2, i.e., human epidermal growth factor receptor 2, is a gene that can play a role in the development of breast cancer.

HER2 receptors are proteins that control how a healthy breast cell grows, divides, and repairs itself. Doctors test HER2 status to see if there are higher than normal levels of this receptor and then term it as HER2 positive cancer.

Targeted therapies generally work best in such cases.

3) Cancer Cell Appearance

This is known as breast cancer grading. In this, the breast cancer cells are carefully observed under a microscope for their appearance.

The ones that look quite similar to normal cells are considered to be slower growing. Contrarily, the ones that look very different will probably grow and spread faster.

• Grade I – Well-differentiated; these resemble normal cells and aren’t growing rapidly
• Grade II – Moderately differentiated; these look somewhat different from normal cells and are growing faster than normal cells
• Grade III – Poorly differentiated; these look like abnormal cells and are multiplying aggressively

Breast Cancer Stages

• Stage 0 – A non-invasive breast cancer such as DCIS (ductal carcinoma in situ). There is no sign of cancer cells invading any nearby tissue.
• Stage 1 – Presence of small tumours usually up to 2 cm but hasn’t spread to lymph nodes yet.
• Stage 2 – Presence of large tumours usually 2 cm to 5 cm which have spread to some surrounding lymph nodes
• Stage 3 – In this larger tumours are present and also probably grow into surrounding tissues like chest wall and skin.
• Stage 4 – Breast cancer that has spread beyond the breasts and has metastasized to other organs of the body is said to be in stage 4.

Breast Cancer Staging Chart

Treatment

Depending on the stage of breast cancer, age and general health of the patient, your doctor will prepare a treatment plan.

Options include:

• Surgery
• Radiation therapy
• Chemotherapy
• Hormone therapy
• Targeted therapy
• Immunotherapy

Every person’s breast cancer is different. The tumour staging helps in evaluating the extent of cancer present and deciding the best suitable treatment option for it.

In Closing

Breast tumour size is undoubtedly the most important deciding factor for breast cancer staging. Early diagnosis holds the key to the efficient and effective treatment of breast cancer. It is important to consult your doctor right away whenever you feel you show any signs or symptoms of breast cancer.