Kenneth L Abbott, MD, FACP  |  5/25/2022

How Worrisome Is My Melanoma?

Not every case of malignant melanoma is alike. Depending on the specific characteristics of the disease as it presents in an individual human being, it can be more or (to a degree) less dangerous. Health care providers consider several factors that determine prognosis (the predicted behavior of the disease) in melanoma, which assists in giving advice to a patient and in designing options for treatment.

The two most important factors in a melanoma lesion that has not spread to other body parts are the thickness of the tumor (the body of cancerous cells) and whether the tumor has ulcerated. Of these two, the thickness or depth of invasion into the skin has the greater ability to predict future behavior. Dermatologists and oncologist use the Breslow scale, developed by pathologist Dr. Alexander Breslow at George Washington University over fifty years ago. This technique measures the thickness of the melanoma tumor in millimeters. After subsequent refinements, the American Joint Commission on Cancer (AJCC) has included Breslow thickness in the method now used to assign a stage to a melanoma lesion. It makes sense that increasing thickness is more dangerous. The thicker a melanoma lesion, the more likely it is to come back, and risk of recurrence has long correlated with risk of death. One key component of this increased risk of recurrence is the likelihood of microscopic spread of melanoma cells to lymph nodes in the area “downstream” from the tumor.

Ulceration is just what it sounds like—the tumor mound develops a central area of erosion, a kind of skin sore, due to cell death. You might think that cancer cells dying is a good thing. However, this development indicates that the tumor is growing faster than it can maintain a blood supply. A cancer cell that spreads beyond the area where it can get oxygen and fuel suffers the same fate as an army that advances into enemy territory past its supply chain. Too bad for the individual cell, but the tumor as a whole is growing and likely spreading rapidly.

When a pathologist examines a removed melanoma lesion under the microscope, she will take care to notice how many cells were actively dividing at the time the specimen was preserved, sliced, and stained. You may recall from high school biology the term “mitosis,” applied to the process of body cell division or duplication. The “mitotic rate” is the number of such visibly dividing cells contained within one square millimeter. While this property has independent prediction ability, the other two discussed above are stronger predictors; this is why they are used in the current staging system. The pathologist will report several other microscopic features after examination we don’t have to consider here.

Some clinical variables that help with prediction of the future course of the disease include the location of the melanoma lesion on the body (people with melanoma on the arms or legs have a lower risk of recurrence than those whose tumors are on their torsos and heads), the age of the patient (older is not so good), and the sex of the affected person (alas, men fare more poorly than women). One of the more important clinical characteristics in 2022 is the spread of the disease to regional lymph nodes. As a consequence, the simultaneous testing of lymph nodes that drain fluid from the region of the melanoma lesion forms a crucial part of the way the disease is treated and can open up options for additional drug treatment after surgery, chiefly using a class of drugs called immunotherapy. Immunotherapy has had a major impact on melanoma outcomes, so much so that I will post a future article on that subject.
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