Stages of Melanoma
When a biopsy has revealed melanoma, the first thing doctors will need to determine is the "stage" of the cancer, which is defined by how large the primary tumor is, and how far the cancer has spread. This is very important because these factors will determine your treatment and outlook for your recovery.
Staging of Melanoma
How the Numbered Stages Are Determined
Clinical information - Describes the overview of all the information gathered through testing and exams (physical exam, x-rays, CT scan, etc)
Pathological information-This combines information from the original biopsy (Breslow depth, ulceration, mitotic rate, Clark level, etc) and biopsies of the lymph nodes and other organs.
Factors for Staging Melanoma
The following factors are gathered from the clinical and pathological information to determine the stage of melanoma:
Tumor Thickness: indicates how deeply the tumor has penetrated the skin. It can be measured in two ways: Breslow Depth and Clark Level.
Breslow Depth: It measures in millimeters how thick the actual primary tumor is. It is measured in millimeters (1 mm= less than 1/16 inch). Breslow depth is measured starting at the outer layer of the epidermis downward to the deepest extension of the melanoma. The thicker the tumor is, the greater the chance it has metastasized or spread to regional lymph nodes or distant sites. It has replaced Clark Level as a more accurate measurement of tumor depth, and is more predictive of prognosis.
Clark Level: It describes how deeply the primary tumor has penetrated the different levels of the skin. The deeper the level of skin it has penetrated, the greater the chance that the tumor has metastasized to regional lymph nodes or distant sites. Clark level uses Roman numerals (I-V) (1-5) to determine the how far within the level the primary tumor has penetrated. Even though Clark Level has officially been dropped by the AJCC as a criteria in determining the stage of a melanoma, because it has been used for over 40 years it will likely continue in usage for some time.
Tumor Ulceration: Ulceration is not the same as skin ulcers, which are open wounds. Ulceration means that, when seen under a microscope, the epidermis (or top layer of the skin) that covers the primary melanoma is not intact. Ulceration cannot be seen with the naked eye. Ulcerated tumors pose a greater risk for metastatic disease than tumors that are not ulcerated.
Mitotic Count (Rate): The number of cancer cells that are in the process of dividing when a pathologist looks at a tissue specimen microscopically. Higher mitotic rates (having more cells that are rapidly dividing) means that the cancer is more likely to grow and spread. In 2010 the AJCC recommended that mitotic count be used as a determining factor in thin melanomas (Stage I).
Number of metastatic lymph nodes: The greater the number of lymph nodes containing melanoma, the less favorable the prognosis.
Microscopic or macroscopic metastasis to the lymph nodes:
- Micrometastases are tiny tumors not visible to the naked eye. They are commonly detected through a microscope after a biopsy of the sentinel lymph node.
- Macrometastases are felt during a physical examination or can be seen by the naked eye when inspected by a surgeon or pathologist. Its presence is usually confirmed by a biopsy or dissection of the lymph node or by being able to see that the tumor extends beyond the lymph node capsule.
- Although progression and risks are different for every patient, in general, macrometastases have a less-favorable prognosis than micrometastases.
Site of distant metastasis: skin vs other areas:
Melanoma that has spread to other areas (distant metastases) of the skin, like the underlying subcutaneous tissue, or distant lymph nodes, have a relatively better prognosis than melanoma that has spread to any other site in the body.
Level of LDH (serum lactate dehydrogenase):
LDH is found in the blood and many body tissues. Higher LDH levels correspond with a greater likelihood that melanoma has spread (metastatic disease) and a less-favorable prognosis than normal LDH levels.
Clark Level and Stage are NOT the same:
- Clark Level - measures how deep the tumor is.
- Stage - measures how far the melanoma has spread.
Note: Clark Level has been replaced by mitotic count as a more accurate predictor of survival and is used in Stage I tumors no more than 1.0mm thick. However, this term may still appear on pathology reports.
- Staging is used to determine which treatment will have the greatest likelihood of success.
- Correct staging is the cornerstone of initiating successful treatment of cancer.
- Stages are labeled using 0 and Roman numerals I through IV (1-4).
- A lower number like I (1) means the melanoma has not spread far.
- The higher the number, the farther it has spread and the more serious the cancer.