Skin Cancer: How Mohs Surgery Can Help

While it may feel nice to soak in the sun on a warm day, the layers of our skin can only protect us so much from the damage of ultraviolet radiation.

“Chronic or intense sun exposure can cause the basal cells in the skin to develop mutations in their DNA, which will get passed along and more mutations develop. The cell will then lose control and continue to grow and destroy the surrounding tissue,” explains Sean Christensen, MD, PhD, a Yale Medicine dermatologic surgeon. “And that is the definition of cancer.”

Skin cancer is typically divided into two types: non-melanoma and melanoma. Non-melanoma skin cancers are most commonly basal cell carcinoma and squamous cell carcinoma. Basal cell carcinoma tends to grow slowly and is unlikely to spread to other parts of the body—but it is persistent in its growth, meaning it can grow to a large size and be destructive to surrounding tissue over a period of years. Squamous cell carcinoma, on the other hand, can spread outside the skin and be lethal, Dr. Christensen says.

But melanoma, though less common than squamous or basal cell carcinoma, is the most concerning type of skin cancer because it has a higher rate of spread and has historically been very lethal at advanced stages, says David J. Leffell, MD, chief of Yale Medicine Dermatologic Surgery and Cutaneous Oncology.

“The good news is that the majority of melanomas are discovered at an early, treatable stage,” Dr. Leffell says.

And that’s where screening comes in. Because skin cancer can look like many things, doctors recommend an annual screening exam with a dermatologist. “Most skin cancers, especially basal cell and squamous cell carcinoma can be cured with surgical removal,” Dr. Christensen says.

This can entail a standard excision where the skin cancer is removed and sent to a pathologist—a process called Mohs surgery. Mohs surgery is often used for skin tumors that have a pattern—seen under the microscope—where they have roots, explains Dr. Leffell. This is common with basal and squamous cell carcinomas, and those fingerlike roots are sometimes missed with standard excision.

With Mohs, a piece of the tumor is removed and examined under a microscope while the patient remains present in the room. Depending on what the doctor sees, more of the concerning area can be removed and studied.

“By making sure we remove all of the tumor we can detect, as well as by preserving any normal tissues and not removing anything more than we need to, we are able to achieve the highest cure rate,” Dr. Christensen says.

Learn more about different types of skin cancer and Mohs surgery in the video above.