Skin Cancer Biopsy: Can You Trust the Results?
May 1, 2019
Dr. Stevan Knezevich, MD, PhD, Board Certified in Dermatopathology, Anatomic and Clinical Pathology. Co-Author of “Pathologists’ diagnosis of invasive melanoma and melanocytic proliferations: observer accuracy and reproducibility study.” BMJ. 2017 Jun 28;357:j2813.
“The interpretation of melanocytic skin lesions is associated with significant variability particularly for lesions ranging from moderately dysplastic/atypical nevi to thin invasive melanomas (pT1a). Surprisingly, the study showed both interobserver and intraobserver variability, meaning that the interpretation was highly subjective and variable between different dermatopathologists interpreting the same lesion and even showed poor reproducibility when the exact same lesion was interpreted a second time by the same dermatopathologist! This variability may be known by some dermatologists, but unfortunately too many clinicians and patients assume the interpretation by a trained specialist results in a definitive evaluation. The criteria for the interpretation of these lesions is, in and of itself, variable, and clearly poorly reproducible, with some dermatopathology fellowships having different philosophical approaches. For example, some institutions believe in the grading of dysplastic nevi (e.g., Mildly dysplastic, moderately dysplastic, and severely dysplastic), while other institutions do not believe in dysplasia or grading at all. As the study involved participants nationwide, and all participants showed poor reproducibility, the findings suggest that it does not matter where one receives their training, the criteria taught in these institutions is poorly reproduced, subjective, and thus, variable.
Two important differences of the DermTech gene expression test for melanocytic lesions is it’s consistent objectivity and reproducibility, both of which are clearly not possible with the current gold standard of having a microscopic evaluation by a board certified dermatopathologist. Your DermTech test result is associated with an overall 99% negative predictive value and less than a 1% chance of missing a melanoma. DermTech detects genomic changes that can’t be seen under a microscope and identifies melanoma in its earliest stages.”