Understanding How Melanoma Is Staged

***The stage of a melanoma is a description of how widespread it is.  It has a lot to do about predicting survival and how treatment should be planned.***

Staging includes such factors as the melanoma’s thickness in the skin, whether it has spread to nearby lymph nodes or any other organs, and certain other factors.  The stage is determined based on the results of the doctor’s examination, the pathology reports on biopsies that have been done, and any imaging tests (CT or MRI scan or PET scan, etc.) or other tests that have been done.

The first several months of my journey fighting melanoma was focused on doing what I needed to do to fight it, to contain it, and to assure the highest probability of both relapse free survival and overall survival.  But staging the cancer was always confusing to me.  For this reason I want to try to take the process and explain it in more simple terms than most usually use.

The best way to fight melanoma is prevention.  So let me start by sharing a slide that categorizes risk factors in terms of the available scientific evidence:

We are all at high risk for melanoma.  This graphic demonstrates primary risk factors of which we must be aware.

We are all at high risk for melanoma. This graphic demonstrates primary risk factors of which we must be aware.

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THE AMERICAN JOINT COMMITTEE ON CANCER (AJCC) SYSTEM

A staging system is a standard way to describe how far a cancer has spread.  The system most often used to stage melanoma is the American Joint Commission on Cancer (AJCC) TNM system.

***It is a complicated system, so be sure to ask your doctor if you have any questions about the stage of your cancer and exactly how that stage was determined.***

You should also ask questions about the relapse free survival rate for each stage and how different treatment options impact it as well as the overall survival rate for each stage of the disease.

The T-N-M system contains 3 key pieces of information:

  • T stands for TUMOR (how far the tumor has grown within the skin and other factors). The T category is assigned a number (from 0 to 4) based on the tumor’s thickness (how far down it has grown). It may also be assigned a small letter (a or b) based on ulceration (skin breakdown) and mitotic rate, which are explained more below.
  • N stands for NEARBY LYMPH NODES (bean-sized collections of immune system cells, to which cancers often spread first). The N category is assigned a number (from 0 to 3) based on whether the melanoma cells have spread to lymph nodes or are found in the lymphatic channels connecting the lymph nodes. It may also be assigned a small letter (a, b, or c), which is also further explained below.
  • M stands for METASTASES.  The M category describes how the melanoma has metastasized (spread) to distant organs, which organs it has reached, and reports on blood levels of a substance called LDH.

There are 2 types of staging for melanoma:

  • Clinical staging is based on what is found during the physical exam, by what is shown by the biopsy and/or removal of the main melanoma, and by any imaging tests that are done.
  • Pathologic staging uses all of this information, plus what is found during biopsies of lymph nodes or other organs if they are done.

***The pathologic stage (determined after the lymph node biopsy) may be higher than the clinical stage (determined before the lymph node biopsy) if the biopsy finds cancer in new areas.  Therefore, what would be a stage II cancer might become a stage III cancer and so on.***

Doctors prefer to use the pathologic stage, if it is available, as it gives a more accurate picture of the extent of the cancer, but in many cases lymph node biopsies are not needed.  Lymph node biopsies are not needed when the clinical information clearly shows that the tumor is localized and has not spread beyond its initial site.  This concept will be further explained later in this post.

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T (TUMOR) categories

The T category is based on the thickness of the melanoma and other key factors seen in the skin biopsy.

Tumor thickness:

The pathologist looking at the skin biopsy measures the thickness of the melanoma under the microscope.

***This is called the Breslow measurement.***

***The thinner the melanoma, the better the prognosis. The thicker the tumor, the worse the prognosis.***

In general, melanomas less than 1 millimeter (mm) thick (about 1/25 of an inch) have a very small chance of spreading.

Mitotic rate:

To measure the mitotic rate, the pathologist counts the number of cells in the process of dividing (mitosis) in a certain amount of melanoma tissue.

***A higher mitotic rate (having more cells that are dividing) means that the cancer is more likely to grow and spread.***

The mitotic rate is used to help stage thin melanomas (T1; see below).

Ulceration:

Ulceration is a breakdown of the skin over the melanoma.

***Melanomas that are ulcerated tend to have a worse prognosis.***

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The possible values for T (TUMOR) are as follows:

  • TX:  Primary tumor cannot be assessed.
  • T0:  No evidence of primary tumor.
  • Tis:  Melanoma in situ. (The tumor remains in the epidermis, the outermost layer of skin.)
  • T1a:  The melanoma is less than or equal to 1.0 mm thick (1.0 mm = 1/25 of an inch), without ulceration and with a mitotic rate of less than 1/mm2.
  • T1b:  The melanoma is less than or equal to 1.0 mm thick. It is ulcerated and/or the mitotic rate is equal to or greater than 1/mm2.
  • T2a:  The melanoma is between 1.01 and 2.0 mm thick without ulceration.
  • T2b:  The melanoma is between 1.01 and 2.0 mm thick with ulceration.
  • T3a:  The melanoma is between 2.01 and 4.0 mm thick without ulceration.
  • T3b: The melanoma is between 2.01 and 4.0 mm thick with ulceration.
  • T4a:  The melanoma is thicker than 4.0 mm without ulceration.
  • T4b:  The melanoma is thicker than 4.0 mm with ulceration.

***The number after the T expresses thickness and the small letter reflects whether or not the tumor has ulceration.***

In my specific case, the primary tumor, which was on my left upper inner thigh, was at least 2.0 mm thick without ulceration.  So it fell in category T2a – a melanoma between 1.01 and 2.0 mm thick without ulceration.  However, while the exact depth could not be determined, it was categorized in the lower category in the absence of clear evidence to place it in the higher category which would have been T3a.

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N (NEARBY LYMPH NODES) categories

The possible values for N depend on whether or not a sentinel lymph node biopsy was done.  I had a sentinel lymph node biopsy performed which provided additional information to stage my particular cancer.  This information also provides additional information when comparing different treatment options that might be available.

***The number after the N reflects how many lymph nodes are involved or whether or not there were malignant cells in the skin around the tumor.*** 

The clinical staging of the lymph nodes, which is done without the sentinel node biopsy, is as follows:

  • NX:  Nearby (regional) lymph nodes cannot be assessed.
  • N0:  No spread to nearby lymph nodes.
  • N1:  Spread to 1 nearby lymph node.
  • N2:  Spread to 2 or 3 nearby lymph nodes, OR spread of melanoma to nearby skin or toward a nearby lymph node area (without reaching the lymph nodes).
  • N3:  Spread to 4 or more lymph nodes, OR spread to lymph nodes that are clumped together, OR spread of melanoma to nearby skin or toward a lymph node area and into the lymph node(s).

***Following a lymph node biopsy, the pathologic stage can be determined, in which small letters may be added to the number.***

  • N1a or N2a means that the melanoma is in the lymph node(s), but it is so small that it is only seen under the microscope.                                                                                   ***Also known as microscopic spread***
  • N1b or N2b means that the melanoma is in the lymph node(s) and was large enough to be visible on imaging tests or felt by the doctor before it was removed.              ***Also known as macroscopic spread***
  • N2c means the melanoma has spread to very small areas of nearby skin (satellite tumors) or has spread to skin lymphatic channels around the tumor (without reaching the lymph nodes).

In my case, the metastatic malignant melanoma cells were identified in two sentinel lymph nodes.  However, these cells could only be seen under the microscope.  So, my N category was N2a – the melanoma is in the lymph nodes but is so small it can only be seen with a microscope.

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M (METASTESES) categories

The M values are as follows:

  • M0:  No distant metastasis.
  • M1a:  Metastasis to skin, subcutaneous (below the skin) tissue, or lymph nodes in distant parts of the body, with a normal blood LDH level.
  • M1b:  Metastasis to the lungs, with a normal blood LDH level.
  • M1c:  Metastasis to other organs, OR distant spread to any site along with an elevated blood LDH level.

LDH is a blood test that measures the amount of an enzyme in the blood called “lactate dehydrogenase” (LDH).  Chemically, LDH is involved in the conversion of pyruvate and lactate in the body.  For example, the accumulation of lactate is the cause of sore muscles after a heavy workout.  In general, the LDH level is measured in order to check for tissue damage, especially to the heart, liver, kidney, skeletal muscle, brain, and lungs — all of which elevates the normally low LDH level in the blood.

For patients with melanoma, the LDH level is used to determine if the cancer may have metastasized  (spread) to organs beyond the skin or lymph nodes; this usually occurs in the liver or lungs.  Although LDH is not specific for melanoma, it may be useful at diagnosis or to monitor post-surgery (adjuvant) treatment.

My initial M category was M0 – no detectable distant spread of the disease.  However, about one year later another lesion was found on my upper inner left arm which is in a different lymph node basin than my primary melanoma.  My LDH level remained within normal limits.  So, my new M category was M1a which includes metastases to the skin and other tissues in distant parts of the body.  This new category changed my cancer stage from Stage IIIB to Stage IV.

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Stage grouping

Once the T, N, and M groups have been determined, they are combined to give an overall stage, using Roman numerals I to IV (1 to 4) and sometimes subdivided using capital letters. This process is called stage grouping.

***In general, patients with lower stage cancers have a better outlook for a cure or long-term survival.***

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STAGE 0 MELANOMA

  • Tis, N0, M0: The melanoma is in situ, meaning that it is in the epidermis but has not spread to the dermis (lower layer).

***Most people who have a Stage 0 Melanoma live the rest of their lives without relapse.***

Others may only need the removal of other small lesions that are benign (without cancer) or in an early stage.  For the prevention of worse future melanomas an individual should conduct periodic careful examinations of their skin for suspicious moles and other lesions.

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STAGE I MELANOMA

Stage IA

  • T1a, N0, M0:  The melanoma is less than 1.0 mm in thickness. It is not ulcerated and has a mitotic rate of less than 1/mm2. It has not been found in lymph nodes or distant organs.

Stage IB

T1b or T2a, N0, M0:  The melanoma is less than 1.0 mm in thickness and is ulcerated or has a mitotic rate of at least 1/mm2, OR it is between 1.01 and 2.0 mm and is not ulcerated.  It has not been found in lymph nodes or distant organs.

Stage I Melanoma

***The probability of a very long relapse free survival period and overall survival is quite high for Stage I melanomas.***

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STAGE II MELANOMA

Stage II melanoma may also be referred to as a “localized tumor”.  All this really means is that there is NO evidence that the tumor has spread beyond the site of the tumor itself.  No lymph nodes are involved and the tissue around the tumor is also free of cancer.

***Chances are excellent for a very long relapse free survival period.***

Stage IIA

  • T2b or T3a, N0, M0:  The melanoma is between 1.01 mm and 2.0 mm in thickness and is ulcerated, OR it is between 2.01 and 4.0 mm and is not ulcerated. It has not been found in lymph nodes or distant organs.

Stage IIB

  • T3b or T4a, N0, M0:  The melanoma is between 2.01 mm and 4.0 mm in thickness and is ulcerated, OR it is thicker than 4.0 mm and is not ulcerated. It has not been found in lymph nodes or distant organs.

Stage IIC

  • T4b, N0, M0:  The melanoma is thicker than 4.0 mm and is ulcerated. It has not been found in lymph nodes or distant organs.

Stage 2 Melanoma

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STAGE III MELANOMA

With Stage III melanoma, there is evidence that the cancer cells have spread beyond the site of the tumor.  One or more lymph nodes or tissues around the site of the tumor contain cancer cells.  But the cancer has not spread to distant sites such as another lymph node basin or the lungs or brain.  Again, relapse free survival rates are very good although they vary between the sub-classes noted below.

***Relapse free survival rates decline from Stage IIIA (where relapse free rates are highest) to Stage IIIC (where relapse free rates are lowest).***

Stage IIIA

  • T1a to T4a, N1a or N2a, M0:  The melanoma can be of any thickness, but it is not ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area, but the nodes are not enlarged and the melanoma is found only when they are viewed under the microscope. There is no distant spread.

Stage IIIB

One of the following applies:

  • T1b to T4b, N1a or N2a, M0:  The melanoma can be of any thickness and is ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area, but the nodes are not enlarged and the melanoma is found only when they are viewed under the microscope.  There is no distant spread.
  • T1a to T4a, N1b or N2b, M0:  The melanoma can be of any thickness, but it is not ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area. The nodes are enlarged because of the melanoma. There is no distant spread.
  • T1a to T4a, N2c, M0:  The melanoma can be of any thickness, but it is not ulcerated. It has spread to small areas of nearby skin or lymphatic channels around the original tumor, but the nodes do not contain melanoma. There is no distant spread.

Stage IIIC

One of the following applies:

  • T1b to T4b, N1b or N2b, M0:  The melanoma can be of any thickness and is ulcerated. It has spread to 1 to 3 lymph nodes near the affected skin area. The nodes are enlarged because of the melanoma. There is no distant spread.
  • T1b to T4b, N2c, M0:  The melanoma can be of any thickness and is ulcerated. It has spread to small areas of nearby skin or lymphatic channels around the original tumor, but the nodes do not contain melanoma. There is no distant spread.
  • Any T, N3, M0:  The melanoma can be of any thickness and may or may not be ulcerated. It has spread to 4 or more nearby lymph nodes, OR to nearby lymph nodes that are clumped together, OR it has spread to nearby skin or lymphatic channels around the original tumor and to nearby lymph nodes. The nodes are enlarged because of the melanoma. There is no distant spread.

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STAGE IV MELANOMA

  • Any T, any N, M1(a, b, or c):  The melanoma has spread beyond the original area of skin and nearby lymph nodes to other organs such as the lung, liver, or brain, or to distant areas of the skin, subcutaneous tissue, or distant lymph nodes.

Once a melanoma has spread to a site located in a different lymph node basin, it does not matter (for staging purposes) if it has spread to nearby lymph nodes nor its thickness.  But typically the melanoma is thick and has also spread to the lymph nodes in the new location.  Survival is also a function of whether the cells have actually spread to other organs or are confined to only distant areas of the skin, tissue or lymph nodes.

The reality of stage IV melanoma is that even if the evidence of disease may go away, it is very likely that cancer cells remain in the body.  And even if those cells do not trigger more cancer now they may trigger other complications.  I suffer from the effects of a paraneoplastic neurological syndrome that was triggered by stage IV melanoma that was confined to a distant skin tumor.  No evidence of the disease currently exists but I am totally disabled and can not work.

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SURVIVAL

The above chart tracks overall survival rates for each stage of Melanoma (I through IV).  Remember that survival may also be predicted by the subclasses within each stage.  And survival is greatly impacted by the treatment options chosen and the diligence of the patient in observing changes that might be occurring even after being declared disease free.

The above chart tracks overall survival rates for each stage of Melanoma (I through IV). Remember that survival may also be predicted by the subclasses within each stage. And survival is greatly impacted by the treatment options chosen and the diligence of the patient in observing changes that might be occurring even after being declared disease free.

Melanoma is a terrible form of cancer.  Treatment options are improving but there is still little evidence that demonstrates that these new treatment options will have a significant impact upon the overall survival rate.  Probably the most promising treatment for metastatic melanoma are tumor specific vaccines that are genetically engineered to attack the specific tumor within each patient.  Hopefully, the future will bring more of these options online and these options will prove beneficial in helping more melanoma patients become lasting cancer survivors instead of long term patients.

Following are links to sites that provide additional information about melanoma staging:

http://www.cancer.org/cancer/skincancer-melanoma/detailedguide/melanoma-skin-cancer-staging

http://www.melanoma.org/understand-melanoma/diagnosing-melanoma/stages-of-diagnosis

http://www.skincancer.org/skin-cancer-information/melanoma/the-stages-of-melanoma/guide-to-staging-melanoma

http://emedicine.medscape.com/article/2007147-overview

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About mcreyscope

Retired / disabled survivor of Stage IV melanoma and paraneoplastic syndrome.
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