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April 25, 2019

Decoding cancer - types, stages, and grades

The world of cancer can be extremely scary and hard to think about for many, whether you or a loved one have had cancer or not. There are over 100 cancers and they all have different grading systems and sub-types, meaning that if you do have cancer, you end up with a very long diagnosis that you may not fully understand. Following this there is a long and complicated ongoing process to choose and assess treatment options, some of which you may never have heard of before being diagnosed with cancer. We’ve written about the different types of specific cancers before, from breast cancer to pancreatic cancer and everything in between. Within this, we have touched on the subjects of cancer grades and some treatments. However, we’ve never done a post on the types, treatments, and terminology behind cancer overall, and feel this could be a very helpful resource if you are in the early stages of diagnosis and are not sure what the terms mean, and what is to come in terms of treatment options. This will be a 2-part blogpost series, with today’s post focussing on diagnosis of cancer, and next week’s on treatment. If you don’t have cancer, we still urge you to educate yourself with these quick summarizing blogposts, as you never know when the information may come in useful for you or a loved one, and with our own health, knowledge is power.

What is cancer?

Let’s start with a basic definition of cancer as a whole. Cancer actually refers to the cells in the body, which is why it can affect any organ or part of the body, even the blood. Some cells begin to grow abnormally and uncontrollably, and they are then considered cancerous, with the ability to spread and attack surrounding areas of the body, and even travel to different parts of the body.

Cancer should not be confused with tumors. Although most cancers involve a malignant (aggressive) tumor that has the ability to spread, tumors themselves are not necessarily cancerous, and a benign (unaggressive) tumor does not have the ability to spread and destroy neighbouring cells.

The different types of cancer

Staging, grading, and metastasis are all terms that you may have heard mentioned where cancer in concerned. They all refer to systems that help categorize cancer, and most cancers fit into this structure. Within those terms there are further sub-systems, so you can imagine it can get quite complex very quickly, and that’s without involving the specific cancer you have e.g. prostate cancer. We’ve broken down the main terms you’ll hear, and there will be some links at the bottom of this post pointing you to further information.

Staging - TNM

A very important part of diagnosing cancer involves staging the cancer, and this determines how far along the cancer is, how large the cancer is, and how likely it is to spread to other parts of the body. To confuse matters, there are 2 main systems that doctors may use, so we will explain both, starting with the TNM system. This stands for Tumor, Nodes, Metastasis.

  • T - The tumor part refers to the size of the growth, where applicable - for cancers where there is no tumor such as blood cancer, this is not always relevant. This is categorized on a scale of 1-4, with 1 being a small tumor.
  • N - Nodes refer to lymph nodes, which are bean-like structures in several areas of the body that are responsible for carrying substances around the body to help with the immune system, as well as filtering out bad substances from the body. If cancerous cells are found in the lymph nodes, it is an indication that the cancer has begun to spread, as these are usually the first to encounter cancerous cells from the primary location. The TNM staging system uses a 0-3 scale here, with 0 meaning no lymph node cells are cancerous.
  • M - The term metastasis means growths have spread to an entirely different part of the body, not just the neighbouring cells or nearby lymph nodes. This suggests the cancer is far along in its progression and harder to treat as it is attacking multiple parts of the body. This part of the staging is simply 1 or 2 -  has not spread to another part of the body, or has, respectively.

Using this system, when receiving a diagnosis, you may see it written down as something like: T2 N1 M1, meaning you have a tumor slightly larger than the smallest tumor but still small, with a low number of cancerous cells in the lymph nodes, and the cancer has not yet spread to another area of the body.

Staging - numbers

This system of staging is similar, but slightly simplified and therefore the one you will hear most people talk about when discussing their cancer diagnosis e.g. ‘I have stage III breast cancer.’ It uses the numbers 1-4, but is usually written out in roman numerals:

  • Stage I - This means the cancer is small and only within the organ it started. Again, for cancers such as blood cancers, the staging is slightly different and we’ve written about blood cancers before.
  • Stage II - The cancer is slightly larger than in stage I, but has not spread into neighbouring tissues yet. In some cancers, stage II can mean the cancer has spread to the lymph nodes to a small degree, but in others, it means it still has not spread at all
  • Stage III - The cancerous growth is now large and has spread to neighbouring tissues and to the nearby lymph nodes.
  • Stage IV - The highest stage of cancer, this refers to a cancer that has spread to an entirely different part of the body, and is also known as secondary cancer, as it has moved from the primary area it started in. You may hear this called metastatic cancer as well, as this refers to the M in the TNM system above.


Some may assume that staging and grading are interchangeable terms, but in fact grading is another step in the diagnostic process for cancer. Grading is important because it looks at the individual cancerous cells at a microscopic level and assesses the way they look and behave.  The grading system can vary slightly for different cancers, but the system most commonly used involves the numbers 1-3, although some cancers have further numbers. Generally speaking:

  • Grade 1 - The cancerous cells are growing very slowly and look very similar to normal cells
  • Grade 2 - The cells don’t look quite normal and are growing at a more accelerated rate than normal
  • Grade 3 - The cells are growing very fast and look extremely abnormal
  • GX - Sometimes the cells cannot be assessed, either because the sample is not enough or they are unsure how the cells are behaving. This is also known as undetermined grade.

It can seem that these staging and grading systems are only there to scare you and give you an idea of how bad your cancer is, but it is actually a very important step and informs how the cancer can be treated. Next week we will be looking at those different treatments in a broad sense, so that you know the kind of terms and treatments that may be offered to you should you be diagnosed with cancer.

Useful links

We’ve put some useful links to our blogposts on specific cancers, as well as some other websites which may help you understand more about cancers and the terms used when diagnosing:

Blood cancers

Bowel cancer

Breast cancer

Cervical cancer

Ovarian cancer

Pancreatic cancer

Cancer Research UK

American Cancer Society


Mandy Tomlinson

Mandy Tomlinson

Mandy has worked for Isabel Healthcare since 2000. Prior to this, she was a Senior Staff Nurse on the Pediatric Infectious disease ward and high dependency unit at one of London's top hospitals, St Mary’s in Paddington which is part of Imperial College Healthcare NHS Trust. Her experience in the healthcare industry for the past 28 years in both the UK and USA means she's a vital resource for our organization. Mandy currently lives and works in Scottsdale, Arizona.


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