Level 1 melanomas are almost always curable by surgical removal of the lesion . Levels 4 and 5 recur in over 85 percent of cases. Level 3 melanomas recur in perhaps 60 percent of patients.
Another classification system (Breslow level) using the exact measurement of the thickness of the tumor under the microscope has recently been introduced and is used together with the other system.
Melanomas less than 0.75 mm are usually considered highly curable by surgery alone, although some people with such "thin" lesions have had recurrences. Tumors 0.76 mm to 1.5 mm are considered to have a moderately deep invasion and have a worse prognosis than thin lesions. Melanomas 1.6 mm or more are very deep, particularly those over 4 mm.
While no exact relationship exists between the two classification schemes, an approximate correlation can be made between levels and thicknesses.
It is prudent to consider any lesion deeper than 0.75 mm potentially recurrent and, therefore, dangerous. Close contact with the surgeon or a medical oncologist for follow-up examinations and scans is required in these circumstances.
The presence of the tumor in regional lymph nodes draining the site of the primary tumor—such as the lymph nodes in the armpit draining a melanoma of the forearm—is another sign of a poor prognosis. Lymph nodes usually provide an immunological barrier against the tumor. When they are filled with tumor, they have obviously lost the battle and cancer cells have usually passed beyond them into the blood and traveled to distant organs. Over 80 percent of patients with involved nodes have a recurrence elsewhere.
