Stages of melanoma

The stage of a melanoma describes how deeply it has grown into the skin, and whether it has spread. The tests you have to diagnose your melanoma will give some information about the stage. In the UK, most melanomas are found at an early stage when the chance of cure is very high. It is important to know the stage because doctors use this to decide on

• The kind of treatment you need
• The likely risk of the melanoma coming back after treatment
• Whether you need tests to see if the melanoma has spread into lymph nodes close to the melanoma.

Doctors use a number of different systems and scales to describe the stages of melanoma

• The Breslow scale looks at the thickness of the melanoma within the skin
• TNM staging of melanoma describes the thickness of the melanoma and whether there is any spread to lymph nodes or other parts of the body
• Number stages of melanoma group together the TNM staging in a simpler way and also according to the treatment needed

Doctors now tend to mostly use TNM staging as it describes the stage of melanoma in the most specific way. For treatment decisions and when talking about stage to patients, doctors tend to use the simpler system of number stages. There is more information about all these staging systems below.

When doctors remove a melanoma they send it to a laboratory. A pathologist then examines the melanoma and measures its thickness with a small ruler, called a micrometer. Measuring the thickness (depth) of the cancer is important. Doctors use a scale called the 'primary tumour thickness scale', which is sometimes called the Breslow thickness. It measures in millimetres (mm) how far the melanoma cells have reached down through the skin from the surface. You can see the structure of the skin in the diagram below.

If your melanoma was less than 1mm thick, it is very unlikely that it will come back. It had not grown deeply enough into the skin for any cells to have gone into the blood vessels and spread. You are unlikely to need any more treatment. But your specialist may want you to come back to the hospital for check ups for a short time.

If your melanoma was thicker than 1mm, there is a chance that it could have spread or could come back in the future. The chance of it coming back will depend on how thick it was, and whether you have any other signs of possible spread, such as enlarged lymph nodes. Your doctor may want to do some more tests. And you will almost certainly have to come back for check ups for the next few years.

Your specialist will take other factors into account when judging your risk of the melanoma coming back, such as how the cells look under a microscope, and whether the skin surface of the melanoma is broken (ulcerated). In the UK, most melanomas are less than 1 mm thick when they are diagnosed, but they can be as much as 10 mm thick. You can ask your doctor to tell you about this tumour thickness, as it is a good guide to whether you might need further surgery or tests, and the chances of the melanoma coming back.

'TNM' stands for Tumor, Node, Metastases. This staging system can describe the size of a primary tumour (T), whether any lymph nodes contain cancer cells (N) and whether the cancer has spread to another part of the body (M).  The 'T' part of the TNM describes the thickness of the melanoma (primary tumour) according to the Breslow scale. 

There are 5 stages of tumour size in melanoma

• Tis - melanoma cells are only in the very top layer of the skin surface
• T1 - the melanoma is less than 1 milllimetre thick
• T2 - the melanoma is between 1 mm and 2 mm thick
• T3 - the melanoma is between 2 mm and 4 mm thick
• T4 - the melanoma is over 4 mm thick

The 'T' part of the TNM system is further divided into two groups, a and b, depending on whether the melanoma is ulcerated or not. Ulcerated means that the covering layer of skin over the tumour is broken. The letter 'a' means not ulcerated and 'b' means ulcerated. So, for example, a melanoma may be T3a or T3b. Ulcerated melanomas have a higher risk of spreading than those which are not ulcerated.

There are 4 possible stages describing whether cancer cells are in the nearby lymph nodes or lymphatic ducts

• N0 - there are no melanoma cells in the nearby lymph nodes
• N1 - there are melanoma cells in one lymph node
• N2 - there are melanoma cells in 2 or 3 lymph nodes
• N3 - there are melanoma cells in 4 or more lymph nodes

The 'N' part of the stage is further divided into groups a, b and c. If the cancer in the lymph node can only be seen with a microscope (micrometastasis) it is classed as 'a'. But if there are obvious signs of cancer in the lymph node (macrometastasis) it is classed as 'b'. The letter 'c' means that there are melanoma cells in small areas of skin very close to the primary melanoma or in the skin lymph channels.

M0 means the cancer has not spread to another part of the body. M1 means the cancer has spread to another part of the body. M1 is further divided into 

• M1a - melanoma cells have spread to skin in other parts of the body or to lymph nodes far away from the where the melanoma started growing
• M1b- melanoma cells have spread to the lung
• M1c - melanoma cells have spread to other organs or cause high blood levels of a chemical produced by the liver (lactate dehydrogenase)

Nearly everyone in the UK with a newly diagnosed melanoma will only have a T stage - that is to say, the melanoma has not spread to any lymph nodes or any other part of the body.

In a very small number of people, after a melanoma has been removed, nodules of melanoma may appear in the skin close to the area of the original melanoma. This is called 'local recurrence'. It occurs when some melanoma cells have broken away from the primary tumour and begun to grow new tumours (nodules) in the surrounding skin. This can happen at any time after the original melanoma has been removed. So it could be some years later. The more time that has gone by since your original diagnosis, the less likely this is to happen.

There are 5 main stages in this system. They are 

Stage 0

This means the melanoma cells are only in the top surface layer of skin cells (the epidermis) and have not started to spread into deeper layers. This stage is also called 'in situ' melanoma.

Stage 1A

The melanoma is less than 1mm thick. The covering layer of skin over the tumour is not broken - it is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

Stage 1B

The melanoma is less than 1mm thick and the skin is broken (ulcerated). Or it is between 1 and 2mm and is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

There is information about the treatment of stage one melanomas in this section of CancerHelp UK.

Stage 2A

The melanoma is between 1 and 2 mm thick and is ulcerated. Or it is between 2 and 4mm and is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

Stage 2B

The melanoma is between 2 and 4mm thick and is ulcerated. Or it is thicker than 4mm and is not ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

Stage 2C

The melanoma is thicker than 4mm and is ulcerated. The melanoma is only in the skin and there is no sign that it has spread to lymph nodes or other parts of the body.

There is information about treatment of stage 2 melanomas in this section of CancerHelp UK.

Stage 3A

The melanoma has spread to 1 to 3 lymph nodes near the primary tumour but the nodes are not enlarged and the cells can only be seen under a microscope. The melanoma is not ulcerated and has not spread to other areas of the body.

Stage 3B

Stage 3B means that 

• The melanoma is ulcerated and has spread to between 1 and 3 lymph nodes nearby but the nodes are not enlarged and the cells can only be seen under a microscope OR
• The melanoma is not ulcerated and it has spread to between 1 and 3 lymph nodes nearby and the lymph nodes are enlarged OR
• The melanoma may or may not be ulcerated, has spread to small areas of skin or lymphatic channels, but nearby lymph nodes do not contain melanoma cells

Stage 3C

Stage 3C means that 

• The melanoma is ulcerated and has spread to between 1 and 3 lymph nodes nearby which are enlarged OR
• The melanoma may or may not be ulcerated and has spread to 4 or more nearby lymph nodes

There is information about treatment of stage 3 melanomas in this section of CancerHelp UK.

Stage 4

These melanomas have spread elsewhere in the body, away from where they started (the primary site) and the nearby lymph nodes. The most common places for melanoma to spread are the lung, liver or brain or to distant lymph nodes or areas of the skin. There is information about treatment of stage 4 melanomas in this section of CancerHelp UK.

In the UK, most melanomas are early stage 1 and are completely cured with surgery. Most stage 2 tumours can also be cured with surgery.