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Dermbits

MD, PhD

How would you compare and contrast the utility of the information from 31-GEP vs. SLNB?

Skin Cancer

So both GEP and sentinel node biopsy are attempting to answer the same question. Is or will this melanoma metastasize distantly? One does it genetically, one does it by actually looking for tumor in the lymph nodes. So the differences that we see are that if we look at sensitivity or how likely if a metastasis is present, is it that the test picks it up? It turns out that GEP is more sensitive. So there are going to be more melanomas called high risk by GEP than by sentinel node biopsy. Probably a couple of reasons. One is that not all, most but not all melanomas do metastasize through the lymphatic. So if you have a melanoma that never goes through, the lymphatics, metastasizes heterogeneously, you may pick that up with GEP, but not by sentinel node biopsy. Now, the flip side of this is that there are going to be cases where a melanoma may have a genetic signal suggesting metastasis, but it doesn't go on to metastasize. Maybe it's treated, maybe it's excised. Maybe the test is over calling it so you'll have more false positives with GEP than you do with sentinel node biopsy.