Hi everyone! Today I want to talk about monitoring precancerous lesions for signs that they may be evolving into cancer. Dermatologists often treat precancerous lesions in the office and a valid question that arises from the patient is how are they to know that the treatment worked and that the precancerous growth no longer poses a threat to become cancer. At times, this is not easy so I hope that I can give some advice to help you between visits to the dermatologist.
An “actinic keratosis” is the most common precancerous growth encountered on sun exposed areas of the body. These growths are precursors of squamous cell carcinoma, with about 5% of actinic keratoses developing into cancer. They appear often as red, scaly areas of skin that do not heal. At times, they can appear as hard wart-like bumps on the skin. The most common treatment for these precancerous lesions is cryotherapy, which is freezing the lesions with liquid nitrogen.
The idea of this treatment is to destroy the top layers of the skin where the sun damaged precancerous cells reside. The areas treated with liquid nitrogen then get red and swollen and then form a blister with the precancerous cells being shed as the blister bursts. Normal skin then heals in and the precancerous skin cells have been killed off and replaced with normal skin cells.
Other treatments include certain creams (imiquimod and 5-fluorouracil) which are applied at home over the course of several weeks to months. These creams tend to cause a lot of irritation and kill off the precancerous cells and then allow for normal skin to heal in.
But how can you tell if these treatments have worked or when to return to the dermatologist? The goal is for complete destruction of the precancerous growth but this is not always achieved, either because not all the precancerous cells are destroyed, or the growth has developed into a skin cancer with abnormal cells that penetrate more deeply than the treatments.
Visually, a thick actinic keratosis is difficult to distinguish from a squamous cell carcinoma and may either be frozen (treated like an actinic keratosis) or biopsied to make sure it is not a skin cancer. If an area is frozen, you should check on it about one month after treatment to evaluate for resolution. Often, it takes more than one treatment to completely treat an actinic keratosis so a particular lesion may be frozen several times before it finally goes away. If the area remains red and scaly, then there are likely residual precancerous cells that need further treatment. If the area grows in size, then there may be underlying skin cancer that should be evaluated.
A hallmark of skin cancer is an area that bleeds or does not heal. So, if after several weeks, the area treated is bleeding or oozing or just will not heal, then return to your dermatologist for evaluation. If you find that a particular lesion is frozen several times without much progress, then discuss having the area biopsied with your dermatologist. Also, compare areas that are treated to see if they appear similarly after treatment. Often, a patient will return after having several lesions frozen and say that most have gone away but there is one that just “does not look right.” And indeed, the one that just does not heal like the others often indicates a skin cancer.