After a melanoma biopsy is performed, and once it is confirmed to be melanoma, there are several systems used for describing how advanced melanoma is (“staging”). These “stages” can inform you as to how serious the condition is, and what type of treatment is best suited for you.
The three main staging systems are(1):
- The Number Stages (i.e “Stage 1” or “Stage 4”). This system uses three measurements, known as TNM, where T is the Thickness of the melanoma, N describes whether the melanoma has spread to the lymphatic system, and M describes whether the melanoma has spread to other areas of the body. The different combinations of T, N and M ratings are translated into your overall Stage.
- The Breslow scale, which essentially describes how thick the melanoma is within the skin
- The Clark scale, which describes how far down, in terms of the different layers of the skin, the melanoma has reached.
The "Stages" (scientifically known as the TNM Scale)The TNM system is the most common across all cancers for categorizing the Stage of the cancer. Determining the “Stage” of melanoma can can help your doctor understand the prognosis, as well as the appropriate treatment options for that Stage.
Melanoma is divided into 5 different stages:
- Stage 1 – There is no evidence that the melanoma has spread and it is highly curable with surgery alone, with a very low risk of recurrence
- Stage 2 – The melanoma is thicker than Stage 1, and the melanoma may have spread to a nearby area of skin, but there isl no evidence of melanoma in the lymph nodes. This melanoma can often be cured with surgery alone, especially if a wide incision is performed.
- Stage 3 – The melanoma is thick and it has spread to the regional lymph nodes. Your doctor will often recommend surgery as well as treatment to help prevent the melanoma from recurring.
- Stage 4 - This is the most serious Stage where the melanoma has spread from the primary site to other areas of the body, and is usually treated with surgery and a variety of strategies, possibly including experimental trial treatments.
Read more about the melanoma Stages, the prognosis, and the TNM scale
The Breslow scaleThe Breslow scale measures the thickness of the tumor in terms of millimeters. Breslow thicknesses are often grouped into categories because studies have shown that the thickness of the tumor is highly predictive of the risk of whether it has spread or will recur once removed. Those categories are often characterized by thickness of tumor in the following way:
< 1mm: Very unlikely that the melanoma has grown deep enough to start spreading
1-2mm: There is some risk that some cells have broken off and begun to spread
2-4mm: The risk that the melanoma has begun to spread is higher
> 4mm: It is a high risk that the melanoma has begun to spread
Note that the thickness of the tumor only measures the risk that it has begun to spread. There are still many tumors greater than 4mm thick that have not started to spread yet. This is why further diagnostic testing is usually warranted by your doctor.
Read more about melanoma and the Breslow scale
The Clark level (or Clark scale)
The Clark scale (often referred to as the “Clark level”) is another way of measuring the thickness of the tumor, however, it is not based on the thickness in millimeters, rather, it is based on how many layers deep in the skin the melanoma has penetrated. There is some debate as to which system of thickness measurement (Breslow or Clark) is more predictive of the risk of spreading of the melanoma, though a major study performed at John’s Hopkins demonstrated that the Breslow thickness was, in almost all cases, much more significantly predictive of risk and outcome. Regardless, the pathology report on a melanoma tumor still often lists the Clark level. The following are the 5 Clark Levels:
Level I: The melanoma is only in the epidermis (also called “in situ”). If completely removed, this type of tumor will not metastas and is generally considered to have a 100% cure rate
Level II: The melanoma has penetrated the second layer of the skin, called the papillary dermis
Level III: The melanoma has penetrated the papillary dermis, and is pressing up against the reticular dermis, which is the third layer of the skin.
Level IV: The melanoma has penetrated the third layer of skin, called the reticular dermis (also sometimes called the “deep dermis”)
Level V: The melanoma has penetrated into the subcutaneous tissue or fat.
One thing that sometimes confuses patients is whether “Stage 1” is the same as “Clark Level I.” The answer is, no. They are two separate systems for categorizing melanoma, and are not related. In almost all cases, your doctor will rely on the Number Stages system (also known as the TNM system) to determine what type course of action is best for you to take.