How is melanoma staged?
A staging system is a standard way to describe how far a cancer has spread. The stage of a cancer is a measure of how widespread it is. The staging of melanoma depends on the following:
- The thickness of the tumor. The thickness is described using the Breslow scale.
- Whether the tumor is ulcerated (has broken through the skin).
- Whether the tumor has spread to the lymph nodes and if the lymph nodes are joined together (matted).
- Whether the tumor has spread to other parts of the body.
The stage is based on the results of physical exams, biopsies, and any imaging tests (CT or MRI scan, etc.) or other tests that have been done. The stage of the melanoma is very important in planning treatment and approximating the prognosis of the patient.
The method used to stage melanoma is based on the thickness of the tumor and whether cancer has spread to lymph nodes or other parts of the body.
There are 2 types of staging for melanoma:
- Clinical staging is based on what is found on physical exams, biopsy/removal of the main melanoma, and any imaging tests that are done.
- Pathologic staging combines all of this information with 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 actually be higher than the clinical stage (determined before the lymph node biopsy) if the biopsy finds cancer in new areas. Clinicians 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.
[34] Information taken from the American Cancer Society
The American Joint Committee on Cancer (AJCC) TNM staging system
The system most often used to stage melanoma is the American Joint Commission on Cancer (AJCC) TNM system. The TNM staging system can be complicated, so ask your clinician if you have any questions about the staging of the melanoma. The TNM system is based on three key pieces of information:
T stands for tumor (how far it 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 and mitotic rate.
N stands for spread to 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 based on its noticed presence in the lymph nodes.
The M category is based on whether the melanoma has spread to distant organs, which organs it has reached, and on blood levels of a substance called lactate dehydrogenase (LDH).
The following stages are used for melanoma:
Stage 0 (Melanoma in Situ)
Stage 0 melanoma in situ. Abnormal melanocytes are in the epidermis (outer layer of the skin).
In stage 0, abnormal melanocytes are found in the epidermis. Abnormal melanocytes may become cancerous and spread into nearby normal tissue. Stage 0 is also called melanoma in situ.
Millimeters (mm): A sharp pencil point is about 1 mm, a new crayon point is about 2 mm, and a new pencil eraser is about 5 mm.
Stage I melanoma. In stage IA, the tumor is not more than 1 millimeter thick, with no ulceration (break in the skin). In stage IB, the tumor is either not more than 1 millimeter thick, with ulceration, OR more than 1 but not more than 2 millimeters thick, with no ulceration. Skin thickness is different on different parts of the body.
In stage I, cancer has formed. Stage I is divided into stages IA and IB.
Stage IA: In stage IA, the tumor is not more than 1 millimeter thick, with no ulceration.
Stage IB: In stage IB, the tumor is either:
- not more than 1 millimeter thick and it has ulceration; or
- more than 1 but not more than 2 millimeters thick, with no ulceration.
Stage II
Stage II melanoma. In stage IIA, the tumor is either more than 1 but not more than 2 millimeters thick, with ulceration (break in the skin), OR it is more than 2 but not more than 4 millimeters thick, with no ulceration. In stage IIB, the tumor is either more than 2 but not more than 4 millimeters thick, with ulceration, OR it is more than 4 millimeters thick, with no ulceration. In stage IIC, the tumor is more than 4 millimeters thick, with ulceration. Skin thickness is different on different parts of the body.
Stage II is divided into stages IIA, IIB, and IIC.
Stage IIA: In stage IIA, the tumor is either:more than 1 but not more than 2 millimeters thick, with ulceration; or more than 2 but not more than 4 millimeters thick, with no ulceration.
Stage IIB: In stage IIB, the tumor is either: more than 2 but not more than 4 millimeters thick, with ulceration; or more than 4 millimeters thick, with no ulceration.
Stage IIC: In stage IIC, the tumor is more than 4 millimeters thick, with ulceration.
Stage III
Stage III melanoma. The tumor may be any thickness, with or without ulceration (a break in the skin), and (a) cancer has spread to one or more lymph nodes; (b) lymph nodes with cancer may be joined together (matted); (c) cancer may be in a lymph vessel between the primary tumor and nearby lymph nodes; and/or (d) very small tumors may be found on or under the skin, not more than 2 centimeters away from the primary tumor.
In stage III, the tumor may be any thickness, with or without ulceration. One or more of the following is true:
- Cancer has spread to one or more lymph nodes.
- Lymph nodes are joined together (matted).
- Cancer is in a lymph vessel between the primary tumor and nearby lymph nodes. The cancer is more than 2 centimeters away from the primary tumor.
- Very small tumors are found on or under the skin, not more than 2 centimeters away from the primary tumor.
Stage IV
Stage IV melanoma: The tumor has spread to other parts of the body.
In stage IV, the cancer has spread to other places in the body, such as the lung, liver, brain, bone, soft tissue, or gastrointestinal (GI) tract. Cancer may have spread to places in the skin far away from where it first started.
Recurrent Melanoma
Recurrent melanoma is cancer that has recurred after it has been treated. The cancer may come back in the area where it first started or in other parts of the body, such as the lungs or liver.
