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Melanoma

Stages Of Melanoma

Last modified: 
29/06/2012 - 14:29

Contributing Author: Guy Slowik FRCS

If a biopsy shows melanoma, it is important for the doctor to determine what stage it has reached before deciding on treatment. Staging involves measuring the thickness of the original tumor and checking to see if it has spread elsewhere. This may require additional tests, including blood tests, chest x-rays, and scans of the bones, liver, and brain.

  • At first melanoma is limited, or localized, to one small place in the body. The tumor is relatively small and thin. Melanoma diagnosed at this early stage usually is growing only in the area of the visible tumor.
  • In more advanced stages of melanoma, the tumor goes deeper into the skin and covers a wider area. It may spread, or metastasize, generally to lymph nodes in the armpit, groin, or other parts of the body.
  • In the most advanced stage, the cancer has spread to other organs in the body.

Why Is Staging Important?

What Factors Are Included In Staging?

What Is The Relationship Between The Stage And Chances of a Cure?

Why Are The Lymph Nodes Important In Diagnosing And Staging Melanoma?

Why Is Staging Important?

The doctor must know the stage of a cancer in order to pick the most effective treatment. Advanced cancer that has spread needs treatment very different from localized cancer growing only in the original tumor site. Staging also helps determine the prognosis, or likely outcome of the disease.

  • Thin melanomas have a more favorable prognosis than thick melanomas.
  • Melanomas that have not spread beyond the original tumor site have a much better prognosis than tumors that have spread to internal organs.
  • If a melanoma is less than 1 millimeter (about 1/25 of an inch) deep, there is only a small chance that it has spread internally. The chances of spread are greater if a melanoma has grown thicker than 1.5 millimeters (about 1/6 of an inch).

Doctors use two terms to describe the thickness of a melanoma.

The Breslow measurement. This involves measuring the actual thickness of the tumor under a microscope using a tiny measuring device. A Breslow measurement of 1 means the tumor has penetrated to a depth of 1 millimeter below the skin's surface.

The Clark level. This uses a scale of I to V to describe a melanoma's depth of invasion. Clark level is not based on a measurement, but on the number of layers of skin that the tumor has penetrated.

  • Clark Level I tumors are still in the epidermis, the outer layer of skin. These are called in-situ lesions.
  • Clark Level II and III tumors have spread to the upper part of the dermis.
  • Clark Level IV tumors have reached the lower part of the dermis.
  • Clark Level V tumors have penetrated into the fatty layer of the skin.

What Factors Are Included In Staging?

Staging of a melanoma takes into account the tumor's thickness, whether it has spread, and how far it has spread. Melanomas generally first spread to nearby lymph nodes. A melanoma on the arm or chest, for instance, may shed cells that go to lymph nodes in the armpit.

The most widely used staging system is the TNM system:

  • T stands for tumor thickness and how far it has spread.
  • N stands for lymph nodes, and whether the tumor has spread to the nodes.
  • M stands of metastasis, and whether the tumor has spread to distant organs.

The TNM system combines information on all three factors to rank a melanoma in stages ranging from 0 to IV:

STAGE

DESCRIPTION

COMMENTS

Stage 0 melanoma.

Cancer cells are found only in the epidermis, the outer layer of the skin.

This is the earliest and most curable stage of melanoma. Doctors may call it Clark Level I melanoma or in-situ melanoma.

Stage I melanoma.

Cancer has spread to the top of the dermis, but not to lymph nodes. The tumor is less than 1.5 millimeters thick.

With the Clark system, such a tumor would be Clark Level II or III.

Stage II melanoma.

Cancer has spread to the bottom part of the dermis, but not to tissue below the skin or to lymph nodes. The tumor is larger, with a Breslow thickness ranging from 1.5 millimeters to 4 millimeters.

It would be a Clark Level IV or V.

Stage III melanoma.

Cancer has spread to lymph nodes near the tumor site.

 

Stage IV melanoma.

Cancer has spread beyond nearby lymph nodes to internal organs.

When melanoma spreads, it usually goes to the lung, liver, or brain.

What Is The Relationship Between The Stage And Chances of a Cure?

Doctors often measure the success of cancer treatment in terms of the five-year survival rate. A person usually is considered cured if he or she is alive and free of any trace of cancer five years after first being diagnosed.

The chances of a cure depend on many factors. One of the most important is the stage of the melanoma when it is diagnosed and treated.

The estimated five-year survival rates for melanoma by stage are:

STAGE

SURVIVAL RATE

Stage 0

virtually 100%

Stage I

over 90%

Stage II

about 80%

Stage III

about 50%

Stage IV

about 20%

The actual outlook for an individual diagnosed with melanoma today may be better than these survival rates suggest. Constant advances in diagnosis and treatment of melanoma make the outlook brighter for today's patients. More current survival rates are now being calculated.

Why Are The Lymph Nodes Important In Diagnosing And Staging Melanoma?

During diagnosis and staging of melanoma, the doctor routinely checks lymph nodes to see if they feel unusually large or hard, indicating that melanoma may have spread there.

If the doctor finds some lymph nodes that are hard or swollen, a fine-needle biopsy or actual removal of the suspicious nodes will be done. A pathologist will examine the biopsy sample to see if they contain cancer cells.

Need To Know:

The lymphatic system is a network of small vessels and nodes that return fluids from body tissues to the blood stream. Lymph is a straw-colored fluid that leaks out of capillaries to bathe tissues and organs of the body. Lymph returns to the blood through a system of lymph vessels.

Located along lymph vessels are lymph nodes, small knots of tissue about the size of a bean that filter the lymph. Nodes contain special cells that fight infections and trap cancer cells.

While lymphatic vessels and nodes are found throughout the body, clusters of nodes are located in the neck, armpits, above the groin, and near some organs and large blood vessels.

The lymphatic system can be a factor in the spread of melanoma because it does the following:

  • Collects fluid that seeps out of capillaries, many of which are near the skin
  • Attempts to filter out and trap abnormal cells, including cancer cells
  • Empties lymph back into the bloodstream through a vein near the heart
  • Has clusters of lymph nodes near organs and major blood vessels

How Are Lymph Nodes Checked For Cancer Cells?

A relatively new procedure called lymph node mapping can determine which lymph node basin(s) drains the area of the tumor. Lymph node mapping involves injecting a blue dye or a harmless radioactive material or both near the tumor site. The injected substance flows along the same pathway and toward the same lymph node as cancer cells would do if spreading from the tumor.

After an hour, the lymph nodes in the area of the tumor site are checked for presence of the injected substance. This mapping can identify the "sentinel" node, the first node in the affected basin where any spreading melanoma cells would be found. The doctor can then perform a sentinel node biopsy on that specific node to determine if melanoma cells are present. If the sentinel node has no cancer cells, then the remaining lymph nodes are unlikely to have cancer cells, thereby eliminating the need to remove them. This is cost effective and spares the patient a major surgical procedure.

Targeting the sentinel nodes can avoid unnecessary removal of lymph nodes and related complications such as lymphedema, a swelling of tissues due to build-up of lymph that can occur following removal of nodes.

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.