Cancer staging is a way to describe how serious the disease is. The five stages of melanoma range from stage 0 (least serious) to stage 4 (most serious).
Your oncologist, a doctor who specializes in cancer, decides how to treat the disease based on its stage.
In this article, you’ll learn what helps define each stage and what staging means in terms of prognosis.
TNM Staging of Melanoma
The American Joint Committee on Cancer (AJCC) melanoma staging system, which came into use on January 1, 2018, is widely used for defining the stages of melanoma.
It’s based on the TNM system, in which each letter refers to specific aspects of melanoma.
“T” Is for Tumor
The T used in melanoma staging refers to how large and thick the growth is. It also indicates if the tumor has ulcerated, or broken through to the skin beneath it.
The T will be followed by a number that corresponds to a specific size and thickness.
After that, there is usually a letter to indicate if the tumor has ulcerated.
An “a” means no ulceration. A “b” means there is ulceration.
“N” Is for Node
The N refers to lymph nodes. When melanoma starts to spread beyond the original tumor, it typically will move to a nearby lymph node or cluster of lymph nodes.
A melanoma that doesn’t involve the lymph nodes will be labeled as N0. A melanoma that does involve the lymph nodes will be labeled as N1, N2, or N3, depending on how many lymph nodes are affected, or if there are local metastases that haven’t yet reached a lymph node.
A letter (“a” to “c”) after a number greater than zero indicates how many (if any) nodes are affected, whether they’re detectable only with biopsy or with a clinical, radiological, or ultrasound examination.
Whether or not a melanoma spreads to one or more lymph nodes, it also may affect nearby skin. Such melanoma tumors are called satellite tumors. They’re defined as being within 2 centimeters (cm) of the original tumor and can be seen without a microscope.
Melanoma tumors also may spread to lymphatic channels, thin tubes that resemble blood capillaries, through which lymph fluid flows.
“M” Is for Metastasis
When cancer cells spread to a part of the body far from the original tumor site, it is said to have metastasized. This can mean the cancer is advanced and may be hard to treat.
The organs melanoma most often spreads to are the lungs, liver, brain, and bones.
A melanoma that has not metastasized is labeled as M0. A tumor that has metastasized is labeled as M1.
A letter (“a” to “c”) after M1 indicates which organs or systems are affected by the metastasis.
Stage 0
A melanoma that’s caught early, while it’s still small and hasn’t affected the skin underneath it, is known as melanoma in situ.
Its size and thickness (T)Whether it has spread to nearby skin or lymph nodes (N)Whether it has metastasized, or spread to distant organs (M)
It may be labeled as stage 0 or Tis.
Melanoma in situ almost always can be cured. It usually is treated with a procedure known as wide excision, in which the tumor and a small amount of the healthy skin around it are removed.
Stage 1
Melanomas in this early stage have not spread to other parts of the body. They are staged based on size, thickness, and whether they have ulcerated.
There are two categories of stage 1 melanoma:
Stage 1A
T1a: The tumor is less than 0. 8 mm in thickness when measured with a microscope and has not ulcerated. T1b: The tumor measures less than 0. 8 mm thick and there is ulceration OR the tumor measures between 0. 8 mm and 1 mm thick with or without ulceration.
Stage 1B
T2a: The tumor measures between 1 mm and 2 mm thick but has not ulcerated.
Stage 2
In stage 2 melanoma, the cancer is larger than in stage 1 and has not spread to other parts of the body. It may or may not have ulcerated.
Stage 2A
T2b: The tumor is between 1 mm and 2 mm in thickness when measured with a microscope and has ulceration. T3a: The tumor measures between 2 mm and 4 mm in thickness but has not ulcerated.
Stage 2B
T3b: The tumor measures between 2 mm and 4 mm in thickness with ulceration. T4a: The tumor measures larger than 4 mm in thickness without ulceration.
Stage 2C
T4b: The tumor measures larger than 4 mm in thickness and has ulcerated.
Stage 3
At this stage, the tumor has affected at least one lymph node and perhaps more. There may or may not be satellite tumors and there may or may not be cancer cells in lymphatic channels. The tumor has not metastasized to other parts of the body.
Stage 3A
The tumor is less than 2 mm in thickness and may or may not be ulcerated. Between one and three nearby lymph nodes are affected, but only to the extent that the cells can be seen with a microscope. It has not metastasized to other parts of the body.
Stage 3B
Either:
There is no evidence of the original tumor or its location is unknown and it has only spread to one nearby lymph node or to small areas of nearby skin.
Or:
The tumor measures no more than 4 mm thickness, may or may not have ulcerated, and has done one of the following:
Spread to only one lymph nodeSpread to small areas of nearby skin or lymphatic channelsSpread to two or three nearby lymph nodes
Stage 3C
There are four possibilities in this stage:
There is no evidence of the original tumor or its location is unknown and it has only spread to one nearby lymph node or to small areas of nearby skin, or to local lymph nodes that are matted (i. e. , grouped together). The tumor measures no more than 4 mm in thickness, may or may not be ulcerated, and cancer cells have spread to many areas of nearby skin or lymphatic channels as well as lymph nodes OR there are cancer cells in four or more lymph nodes or clumps of lymph nodes. The tumor measures between 2 mm and 4 mm in thickness with ulceration OR is thicker than 4 mm with no ulceration. There are cancer cells in one or more nearby lymph nodes and/or small areas of nearby skin or lymphatic channels. The tumor is thicker than 4 mm and is ulcerated and has reached one to three lymph nodes that are not clumped together OR has spread to small areas of skin or lymphatic channels and may or may not have reached one lymph node.
Stage 3D
The tumor is thicker than 4 mm and ulcerated and has spread to:
Four or more lymph nodes or to a nearby clump of lymph nodesSmall areas of skin or lymphatic channels as well as at least two nearby lymph nodes or nodes that are clumped together
Stage 4
Stage 4 is the most advanced stage of melanoma. It’s the only stage in which cancer cells have spread to one or more distant body parts.
Once this happens, the melanoma is given a stage 4 classification no matter how big the original tumor is, whether there are satellite tumors, or whether any lymph nodes or lymphatic channels are affected.
Melanoma Survival Rates
There’s no way to predict exactly how a disease like melanoma will progress for an individual person because some people have cancer that advances rapidly from one stage to another, and not everybody’s cancer responds to treatment in exactly the same way. Your underlying health may play a role too.
That said, most experts talk about melanoma outcomes in terms of five-year survival rate.
Cancer experts base five-year survival rates for melanoma on information from the National Cancer Institute’s Surveillance, Epidemiology, and End Results Program database (SEER).
Survival statistics from the SEER database are not based on AJCC melanoma staging. Instead, they’re based on if and how far the melanoma has spread:
Summary
Healthcare providers use the TNM staging system to define the severity of a case of melanoma. Knowing this allows them to figure out the best way to treat the disease.
This system looks at three specific aspects of a melanoma: tumor size and depth (T), lymph node involvement (N), and metastasis (M).
The five stages of melanoma are based on this information. The earliest, stage 0, is highly curable. The most advanced, stage 4, tends to be challenging to treat.
Five-year survival rates for melanoma are based on whether the cancer has spread and to what degree.
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