Staging is used to describe extent of cancer into body. It often includes information about the size of the tumour, which parts of the organ have cancer, whether the cancer has spread to lymph nodes (metastasized) and where it has spread etc
Why staging is required?
Staging helps cancer specialists to
• plan treatment
• predict a person’s chance of recovery
• predict how the treatment plan will work
• to study and compare in clinical trials
How are cancer staged?
There are various staging systems used for different types of cancers. The most common staging system is TNM system used to stage most solid tumour cancers like breast cancer or prostate cancer. TNM stands for tumour, node (lymph node) and metastasis. It is used to stage most solid tumour cancers.
In this staging system, a number will follow each letter which signifies the extent of the cancer in each category.
Primary tumour (T)
- TX: Main tumour cannot be measured.
- T0: Main tumour cannot be found.
- T(is), or T in situ: The tumour is still within the confines of the normal glands and cannot metastasize.
- T1, T2, T3, T4: Refers to the size and/or extent of the main tumour. Higher is the number, larger is the size of tumour or more it has spread in nearby areas. It can be further divided.
Regional lymph nodes (N)
The function of lymphatic fluid is to transport immune system cells throughout the body. Lymph nodes help to move this fluid. Cancer often first spreads to and through nearby lymph nodes.
- NX: Cancer in nearby lymph nodes cannot be measured.
- N0: Cancer has not spread to lymph nodes.
- N1, N2, N3: It is used to refer the number and location of lymph nodes that contain cancer. Higher the number after the N, more lymph nodes that contain cancer.
Distant metastasis (M)
Metastasis is the spread of cancer to other parts of the body.
- MX: Metastasis cannot be measured.
- M0: Cancer has not spread to other parts of the body.
- M1: Cancer has spread to other parts of the body.
What are types of TNM staging?
Solid tumour cancers may be given both a clinical and pathologic stage.
1. Clinical stage is given before treatment and is given based on the results of exams and tests, such as imaging tests, done at the type of diagnosis. Mostly doctors choose a treatment based on the clinical stage. It is shown by a lowercase “c” before the letters TNM on some medical reports.
2. Pathologic stage is based on the results of tests and exams done when learned about the cancer during surgery and when looking at the tissue after it is removed by surgery. It gives more knowledge of cancer. The pathologic stage is shown by a lowercase “p” before the letters TNM on a pathology report.
What is stage grouping?
TNM description is grouped into stage from 0 to 4 for many types of cancer. Higher the number, the more the cancer has spread.
- stage 0 – It is a precancerous change. In this stage abnormal cells are formed but haven’t spread.
- stage 1 – the tumour is usually small and hasn’t spread outside the organ
- stages 2 and 3 – the tumour is larger or has spread outside of the organ.
- stage 4 – It is advanced stage and cancer has spread through the blood or lymphatic system to a distant organs in the body (metastatic spread)
What is a cancer grade?
A cancer’s grade describes how cancer cells and tissue look when observed under a microscope when compared to healthy cells. More the abnormality of cell, higher is the cancer grade. Lower grade cancers are typically less aggressive and have a better prognosis whereas high grades tend to be more aggressive.
Some cancers have their own system for grading tumors. Many others use a standard 1-4 grading scale.
- Grade 1: Tumour cells looks most like healthy cells and tissue. These are called well-differentiated tumours and are considered low grade.
- Grade 2: The tumour cells and tissue are somewhat abnormal as compared to healthy cells and are called moderately differentiated.
- Grade 3: Cancer cells and tissue look very abnormal. These cancers are considered poorly differentiated, since they no longer have an architectural structure or pattern.
- Grade 4: These undifferentiated cancers have the most abnormal looking cells. These cells have tendency to spread faster.