After melanoma has been diagnosed, tests are done to find out if cancer cells have spread within the skin or to other parts of the body.
The process used to find out whether cancer has spread within the skin or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. Talk with your doctor about what the stage of your cancer is.
The following tests and procedures may be used in the staging process:
- Physical exam and history. An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
- Lymph node mapping and sentinel lymph node biopsy. Procedures in which a radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through lymph ducts to the sentinel node or nodes (the first lymph node or nodes where cancer cells are likely to have spread). The surgeon removes only the nodes with the radioactive substance or dye. A pathologist views a sample of tissue under a microscope to check for cancer cells. If no cancer cells are found, it may not be necessary to remove more nodes.
- CT scan (CAT scan). A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography. For melanoma, pictures may be taken of the chest, abdomen, and pelvis.
- PET scan (positron emission tomography scan). A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
- Blood chemistry studies. A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. For melanoma, the blood is checked for an enzyme called lactate dehydrogenase (LDH). LDH levels that are higher than normal may be a sign of melanoma.
The results of these tests are viewed together with the results of the tumor biopsy to find out the stage of the melanoma.
Spreading of Melanoma
There are three ways that cancer spreads in the body.
The three ways that cancer spreads in the body are:
- Through tissue. Cancer invades the surrounding normal tissue.
- Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
- Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.
When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.
The method used to stage melanoma is based mainly on the thickness of the tumor and whether cancer has spread to lymph nodes or other parts of the body.
The staging system is based on the following:
- The thickness of the tumor. The thickness is described using the Breslow scale.
- Whether the tumor is ulcerated (has broken 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.
Stage 0 (Melanoma in Situ)
In stage 0, abnormal melanocytes are found in the epidermis. These abnormal melanocytes may become cancer and spread into nearby normal tissue. Stage 0 is also called melanoma in situ.
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 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.
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 may be joined together (matted).
- Cancer may be in a lymph vessel between the primary tumor and nearby lymph nodes.
- Very small tumors may be found on or under the skin, not more than 2 centimeters away from where the cancer first started.
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.
Last updated June 4, 2013.
Reference: National Cancer Institute