What if you find a lesion that you believe could be melanoma? See your doctor right away. Early diagnosis can be life-saving.

The only way to diagnose a melanoma with certainty is to examine the tissue under a microscope -- a procedure called a biopsy.

The most important information the doctor gets from a biopsy is:

• Is the lesion a melanoma, another type of skin cancer, or is it benign (non-cancerous)?
• If the lesion is melanoma, how thick is it -- that is, how deeply has it penetrated into the skin? 

The thickness of the melanoma is critical information, both for the planning of therapy and for informing the patient just how serious the disease may be. Thickness of tumor is related to the statistical survival rate after tumor removal.

The deeper into the skin the tumor penetrates, the more likely is the possibility that the tumor has spread or metastasized through lymph channels to lymph nodes, or via blood vessels to internal organs.

A tumor confined to the very top layer of the skin (the epidermis) is said to be "in situ" -- meaning it has not penetrated below the top layer into the second layer of the skin. 

Two systems have been developed to relate the degree of penetration of melanoma into the skin to 5-year survival after surgical removal of the melanoma. The older system is called "Clark Level" after its originator, Dr. Wallace Clark. In the Clark system, there are five levels defined, each associated with a shorter post-removal survival time than the level above it. Clark Level I is melanoma "in situ", that is typically cured by removal. Clark Level V is melanoma that has invaded through the superficial layers of the skin to the underlying fatty layer, and is associated with the shortest probable survival after melanoma removal.

The newer system of Breslow thickness, named after its originator Dr. Alexander Breslow, is in wider use today. In the Breslow system, for example, invasive tumor thickness of less than 0.76 millimeters is associated with a 5-year survival of 97% of patients; a tumor thickness of more than 8.0 millimeters is associated with 5-year survival of 32% in patients. Click on Thickness for a discussion of Breslow thickness.

Tumor thickness also is the determining factor in how much tumor-free tissue (margin) is removed from tissue surrounding the melanoma, at the time of surgery. Thicker tumors require removing with wider margins in an attempt to prevent recurrence. For example, a melanoma in situ requires removal of a tumor-free margin of one-half a centimeter. A melanoma more than 4 millimeters thick requires removal of at least 2 centimeters of tumor-free tissue from around the melanoma site to be certain of complete tumor removal. Click on Margin for a discussion of the relationship between tumor thickness and margin.

A future edition of MelanomaNet will discuss the systems used in classifying the stages of metastatic melanoma. Tumor staging is used in planning tumor therapy ranging from surgery to chemotherapy and other treatments for metastatic melanoma.