Melanoma Stages, the prognosis, and the TNM scale
The "Staging" system (more properly known as the TNM system) is the most common system across all cancers for categorizing the Stage of the cancer. The fundamentals of the system are similar across cancers, though the specific rules are particular for the type of cancer being considered.
The purpose of determining your “Stage” of melanoma, is so that you and your doctor can understand the prognosis, as well as the appropriate treatment options for that Stage. Melanoma is divided into 5 different stages:
Stage 0 – The melanoma is only on the top layer of the skin and has not begun to spread to other layers. At this stage, the melanoma is 100% treatable with surgery and has a very low likelihood of returning once removed.
Stage 1 – The melanoma is thicker, and could protrude past the first layer of skin. However, there is no evidence of any further spreading, and no lymph notes show any sign of being affected. Melanoma of this stage is also highly curable with surgery alone, with a low risk of recurrence or spreading once removed.
Stage 2 – The melanoma is thicker than Stage 1, and could affect several layers of the skin. There is still no evidence of melanoma in the lymph nodes. The melanoma may have spread to the surrounding skin area, but there is no evidence of any spreading beyond this. This melanoma can often be cured with surgery alone, especially if a wide incision is performed. Your doctor may recommend additional treatment as a preventative measure, as this Stage of melanoma is at risk for recurrence and spreading.
Stage 3 – The melanoma is thick and it has spread to the regional lymph nodes. Your doctor will often recommend surgery to remove the primary melanoma, and any other sign of melanoma tumors, including the lymph nodes in the region where the melanoma has spread. Your doctor will also likely recommend treatment to help prevent the melanoma from recurring. This stage of melanoma has a more significant risk of reoccurrence, and can sometimes spread to other areas of the body.
Stage 4 – The melanoma has spread from the primary site to other areas of the body, including other limbs, or organs such as the brain, lungs, and liver. In many cases surgery can be used to remove all of the melanoma tumors. Your doctor will also likely recommend treatment, possibly including experimental trial treatments, to help stop tumor growth, stop tumor spreading, and prevent reoccurence.
These Stages are further split based on a number of factors (ex. Stage 1A or Stage 3B, etc.). Check out this chart below for a detailed summary of the different stages, or read about the various components that determine Stage in detail below.
“T” designationThe “T” in the TNM scale stands for “Thickness” of the melanoma, and is broken into the following categories:
- T1 - less than 1mm thick
- T2 - between 1 mm and 2 mm thick
- T3 - between 2 mm and 4 mm thick
- T4 – over 4 mm thick
Note that a melanoma will also be categorized at T4, even if it is less than 4mm thick IF there are groups melanoma cells in the surrounding skin less than 5 cm from the primary melanoma.
In addition the T scale has a further component which describes whether the melanoma is ulcerated or not. As described above, an ulcerated tumor suggests a higher risk of spreading and relapse:
- a – the melanoma is ulcerated
- b – the melanoma is NOT ulcerated.
In summary, the “T” designation will have 3 characters. For example a designation of T1a means the melanoma is less than 1mm thick and is ulcerated.
“N” DesignationThe 'N' in the TNM scale stands for whether or not the lymph nodes or lymphatic ducts contain melanoma cells. The categories are:
- N0 – no lymph nodes show any sign of melanoma
- N1 - one lymph node has been found with melanoma
- N2 – EITHER 2-3 lymph nodes have been found with melanoma OR the melanoma has spread toward a nearby lymph node area, without reaching the lymph nodes.
- N3 – EITHER 4 or more lymph nodes have been found with melanoma OR the melanoma has spread to at least one lymph node and has been detected in tumors between the primary site of the melanoma, and the lymph node areas.
In addition the “N” scale has a further component which describes them:
- a - the melanoma in the lymph node can only be seen with a microscope
- b – the melanoma in the lymph node can be seen with the naked eye
- c- the melanoma has spread towards the lymph nodes (these are called “in transit metastases”), and the in transit tumors are at least 5cm away from the original (or “primary”) melanoma site.
“M’ DesignationThe “M” in the TNM scale stands for whether or not the melanoma has spread to a distant area of the body. Generally, a distant area is one that is beyond the local lymph nodes, and hence, another area of your body. For example, spreading from an arm to a leg would be a distant spreading. The “M” categories are:
- M0 - there is NO sign of melanoma in any distant areas of the body * M1 - there IS melanoma in another part of the body
In addition, the “M” scale has a further component which only applies to M1 and describes it further:
- M1a: The melanoma has spread to distant skin or subcutaneous tissue (the tissue directly below the skin) OR it has spread to distant lymph nodes.
- M1b: The melanoma has spread to the lung.
- M1c: The melanoma has spread to other organs, OR the melanoma has spread to distant skin or other area and the patient has an elevated blood LDH level. Note that an elevated LDH level is a sign that there may be larger tumors or multiple sites of cancer in the body.
Summary of Staging
The combination of the different T N and M scales determine the overall Stage of melanoma.
[Note: I will insert the chart once images are supported on the site]
Each Stage of melanoma has both an associated state of risk (i.e. what are the chances of survival based on statistics of other people who had that same stage of melanoma). They also are informative in terms of what treatments your doctor may consider for you, and what experimental treatments you may be eligible to participate in.
See Prognosis to learn more about the survival rates at various stages.
References (1) http://www.cancerhelp.org.uk/help/default.asp?page=3015#stage1 (http://www.cancerhelp.org.uk/help/default.asp?page=3015#stage1)