Staging is a process of finding out how widespread a cancer is. This includes describing its size as well as whether it has spread to the lymph nodes or any other organs. The tests described in the section, "How is melanoma diagnosed?" are the ones used to help determine the stage of the melanoma.

A staging system is a standard way of summarizing how far a cancer has spread. This helps members of the cancer care team to plan appropriate treatment and determine a patient's prognosis (outlook).

The American Joint Committee on Cancer (AJCC) TNM System

The system most often used to stage melanoma is the American Joint Commission on Cancer (AJCC) TNM system. Several tests and procedures are used to assign T, N, and M categories and a grouped stage. The TNM system for staging contains 3 key pieces of information:

• T stands for tumor (its size and how far it has spread within the skin). The T category is assigned a number (from 0 to 4) based on the tumor's thickness (how far down it has grown). It is also assigned a small letter "a" if it is not ulcerated or a "b" if it is ulcerated. Ulceration means the layer of skin covering the melanoma is absent. This is seen under a microscope after a biopsy.

• N stands for spread to nearby lymph nodes (small bean-shaped collections of immune system cells that help the body fight infections and cancers). 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 is also assigned a small letter: "a" if melanoma cells can only be seen with the microscope or "b" if they can be seen with the naked eye. A letter "c" is assigned if there are very small areas of melanoma in the nearby skin or if the melanoma is in skin lymphatic channels around the tumor (but not in the nodes themselves).

• The M category is based on whether the melanoma has metastasized (spread) to distant organs, which organs it has reached, and sometimes on blood levels of a substance called LDH.

There are actually 2 types of staging for melanoma:

• Clinical staging is done based on what is found on physical exam, biopsy of the melanoma, and 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. Therefore, the clinical stage (determined before the node biopsy) may actually be lower than the pathologic stage (determined after the node biopsy).

T categories

The T category is based on the thickness of the melanoma seen in the skin biopsy. This is an important part of determining a patient's prognosis.

The pathologist looking at the skin biopsy measures the thickness of the melanoma under the microscope with a device called a micrometer, which is like a small ruler. This technique is called the Breslow measurement. The thinner the melanoma, the better the prognosis. In general, melanomas less than 1 millimeter (mm) in depth (about 1/25 of an inch or the diameter of a period or a comma) have a very small chance of spreading. As the melanoma becomes thicker, it has a greater chance of spreading.

Another system, called the Clark level, describes how far a melanoma has penetrated into the skin instead of actually measuring it. The Clark level of a melanoma uses a scale of I to V (with higher numbers indicating a deeper melanoma) to describe whether:

• the cancer stays in the epidermis (Clark level I)
• the cancer has begun to invade the upper dermis (Clark level II)
• the cancer involves most of the upper dermis (Clark level III)
• the cancer has reached the lower dermis (Clark level IV)
• the cancer has invaded to the subcutis (Clark level V)

The Breslow measurement of thickness is generally thought to be more useful than the Clark level of penetration in determining a patient's outlook. The thickness is easier to measure and depends less on the pathologist's judgment. But sometimes the Clark level shows that a melanoma is more advanced than doctors may think it is from the Breslow measurement. The Clark level is used to stage thin melanomas (T1; see below).

In either system, the melanoma tends to have a worse prognosis if the pathologist says it is ulcerated (outermost covering layer of skin is absent).

Using these systems, the possible values for T are:

TX: Primary tumor cannot be assessed.

T0: No evidence of primary tumor.

Tis: Melanoma in situ (Clark level I - it remains in the epidermis).

T1a: The melanoma is less than or equal to 1.0 mm thick (1.0 mm = 1/25 of an inch), without ulceration and Clark level II or III.

T1b: The melanoma is less than or equal to 1.0 mm thick, Clark level IV or V, or with ulceration.

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.

N categories

The possible values for N depend on whether or not a sentinel lymph node biopsy was done.

The clinical staging of the lymph nodes is listed below; it is done without the sentinel node biopsy.

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. The involvement of any lymph nodes can be subdivided as follows:

• Any Na (N1a, N2a, etc.) means that the melanoma in the lymph node is only seen under the microscope.

• Any Nb (N1b, N2b, etc.) means that the melanoma in the lymph node is visible to the naked eye.

• 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).

M Categories

The M values are:

MX: Presence of distant metastasis cannot be assessed.

M0: No distant metastasis.

M1a: Distant metastases to skin or subcutaneous (below the skin) tissue or distant lymph nodes.

M1b: Metastases to lung.

M1c: Metastases to other organs, OR distant spread to any site along with an elevated blood LDH level.

Stage grouping

Using the TNM system, a doctor will use each letter (T, N, and M) and a corresponding number. For example, a melanoma could be staged as T2, N0, M0.

To make this information somewhat clearer, several of these TNM descriptions can be grouped together into a simpler set of stages, labeled stage 0 through stage IV. This process is called stage grouping. The stage is described using 0 and Roman numerals from I to IV, and is sometimes subdivided using capital letters. In general, patients with lower stage cancers have a better outlook for a cure or long-term survival.

Stage 0

Tis, N0, M0: The melanoma is in situ, meaning that it involves the epidermis but has not spread to the dermis (lower layer). This is also called Clark level I.

Stage IA

T1a, N0, M0: The melanoma is less than 1.0 mm in thickness and Clark level II or III. It is not ulcerated, appears to be localized in the skin, and 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 Clark level IV or V, or it is between 1.01 and 2.0 mm and is not ulcerated. It appears to be localized in the skin and has not been found in lymph nodes or distant organs.

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 appears to be localized in the skin and 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 appears to be localized in the skin and 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 appears to be localized in the skin and has not been found in lymph nodes or distant organs.

Stage IIIA

T1a-4a, N1a or N2a, M0: The melanoma is not ulcerated. It has spread to 1-3 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. The thickness of the melanoma is not a factor, although it is usually thick in people with stage III melanoma.

Stage IIIB

T1b-4b, N1a or N2a, M0: The melanoma is ulcerated. It has spread to 1-3 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-4a, N1b or N2b, M0: The melanoma is not ulcerated. It has spread to 1-3 lymph nodes near the affected skin area. The nodes are enlarged because of the melanoma. There is no distant spread.

T1a/b-4a/b, N2c, M0: The melanoma can be ulcerated or not. 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

T1b-4b, N1b or N2b, M0: The melanoma 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.

Any T, N3, M0: The melanoma can be ulcerated or not. 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.

Stage IV

Any T, Any N, M1: 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 or lymph nodes. Neither the lymph node status nor thickness is considered, but typically the melanoma is thick and has also spread to lymph nodes.

Survival rates by stage

The stage of the melanoma has a major effect on a person's outlook for survival. The following survival rates are based on a study of more than 40,000 patients who were diagnosed between 1988 and 2001.

There are some important points to note about these numbers:

• The 5-year and 10-year survival rates refer to the percentage of patients who live at least 5 or 10 years after being diagnosed. Many of these patients live much longer than this.

• While these numbers are among the most current we have available, they represent people who were first diagnosed and treated many years ago. Improvements in treatment since then mean the survival rates for people now being diagnosed may be higher.

• There are ranges of survival rates within some of the stages because they include different T and N categories. Even within a stage, those with less advanced disease are likely to have a better prognosis.

• While survival statistics can sometimes be useful as a general guide, they may not accurately represent any one person's prognosis. A number of other factors, including other tumor characteristics and a person's age and general health, can also affect outlook. Your doctor is likely to be a good source as to whether these numbers may apply to you, as he or she is familiar with the aspects of your particular situation.

Stage IA: The 5-year survival rate is around 99%. The 10-year survival is around 97%.

Stage IB: The 5-year survival rate is around 92%. The 10-year survival is around 86%.

Stage IIA: The 5-year survival rate is around 78%. The 10-year survival is around 66%.

Stage IIB: The 5-year survival rate is around 68%. The 10-year survival is around 59%

Stage IIC: The 5-year survival rate is around 56%. The 10-year survival is around 48%

Stage IIIA: This was a new stage when the study was done, so 5- and 10-year survival rates were not available for this group. The rates would most likely fall in between the stages above and below.

Stage IIIB: The 5-year survival rate ranges from around 50% to around 68%. The 10-year survival ranges from around 44% to around 60%.

Stage IIIC: The 5-year survival rate ranges from around 27% to around 52%. The 10-year survival ranges from around 22% to around 37%.

Stage IV: The 5-year survival rate for stage IV melanoma is about 18%. The 10-year survival is 14%. It is higher if the spread is to skin or distant lymph nodes rather than to other organs.

Other factors affecting survival

Other factors aside from stage may also affect survival. For example, stage for stage, older people generally have shorter survivals. The biggest drop begins at age 70. Recent reports also show that when melanoma occurs in African Americans, although uncommon, survival is shorter than when it occurs in whites. Some studies have shown that melanoma is more serious if it occurs on a foot, palm, or nail bed. People with HIV infection and melanoma also are at greater risk of dying of their melanoma.