How Gene Expression Profiling Works in Skin Cancer, with David Cotter, MD, PhD

In a session presented during the Dermatology Education Foundation (DERM) 2025 NP/PA CME Conference in Las Vegas, David Cotter, MD, PhD, of Las Vegas Dermatology, spoke about gene expression profiling of skin cancer.1

Cotter highlighted the integration of artificial intelligence (AI) and molecular testing in dermatology, specifically gene expression profiling, which examines gene activity in cells to predict behavior. He noted that the technique can be applied to single cells or tumor tissues, aiding in clinical decisions, such as risk stratification for those with melanoma via the I-31 gene expression profiling (GEP) test.

“Molecular testing in dermatology sounds complicated, but it's really simple,” Cotter explained. “It just means the testing of molecules in the skin. The way that we're going to be talking about that this year is looking at gene expression profiling. All gene expression profiling is a molecular technique that lets you look at what genes are turned on or off within a cell, and based on that, you can make predictions about the cellular behavior. Broad strokes, you can do this all the way down to the single cell level.”

Cotter clarified that gene expression profiling is not genetic testing but rather a genomic test focusing on RNA levels.

“Broadly, you can look at tumor tissue in mass and ask what the entire milieu of the gene expression is,” Cotter said. “You can even laser-dissect out certain parts of a tumor. Just look at tumor cells. Look at fibroblasts, keratinocytes, or the immune cells that are making up that tumor, and ask, ‘How are the genes turned on or off?’ And depending on what your question is or what clinical application you're thinking of, you may want to approach it one way or another.”

Cotter was also asked about how to approach patients in any discussions about gene expression profiling.

“The way that I usually approach the topic is, I say, ‘First of all, it's a really good thing you came in, as we biopsied that funny brown spot, and unfortunately, it came back as a melanoma,’” Cotter said. “We'll talk about what their stage is and what that means for them. But then I also tell them I'm going to order an additional molecular test that's going to give me insights into how the melanoma specifically is behaving. I tell them that I need to know everything that there is potentially to know about the melanoma so we can help answer any questions that come up, giving the best, highest level of care if patients are worried about ‘genetic testing.’”

To find out more about the topics highlighted in this interview, view Cotter’s full video segment above. For more presented at DERM 2025, view the latest conference coverage.

The quotes used in this interview summary were edited for clarity.

1. Cotter D. Dark Waters: Navigating the Diagnosis of Melanoma and Gene Expression Profiling of Skin Cancer. Presented at DERM 2025 NP PA CME Conference; July 23-26, 2025; Las Vegas, Nevada.