Abstract:

The DermTech Pigmented Lesion Assay (PLA) is a genomic test that uses tape-stripping to detect expression of Linc00518 and PRAME, RNA biomarkers associated with melanoma. We sought to compare PLA PRAME expression with conventional immunohistochemical staining (IHC) for PRAME protein in standard Formalin-Fixed Paraffin Embedded (FFPE) biopsies. We studied de-identified samples of FFPE skin biopsies obtained between April 1, 2019 and April 1, 2022, which had undergone PLA. We obtained information on baseline demographic and pathologic information, including age, sex, location of biopsy, and diagnosis. PLA PRAME was either detected or not detected. IHC PRAME nuclear staining was scored as no staining (0), 1%–25% (1+), 26%–50% (2+), 51%– 75% (3+), or 76%–100% (4+). Staining of 1%–50% of tumor cells was considered “focally positive.” Staining of >50% was considered “positive.” The study included a total of 102 patients with 45 (44%) male patients and 57 (56%) female patients with an average age of 40.8 years. The diagnoses included invasive melanoma (2), melanoma in situ (2), severely dysplastic nevus (2), moderately dysplastic nevus (44), mildly dysplastic nevus (38), atypical melanocytic proliferation (4), benign nevus (7), lentigo (2), and seborrheic keratosis (1). Overall, PLA detected PRAME in 47 (46%) cases and IHC detected PRAME was positive (3+ or 4+) in 11 (11%) cases. We found an association between PLA detected PRAME and immunohistochemical staining of 3+ or 4+ (Fisher’s exact test, p=0.002), as well as a positive correlation between PLA detected PRAME and immunohistochemical stains graded 0-4 (Spearman’s rank correlation, rho = 0.4318, p <0.001). PLA sensitivity was 86% and specificity was 56%. While limited by the small sample size from a single center, the data suggests there is correlation between IHC and PLA detected PRAME.

Financial Disclosure:
No current or relevant financial relationships exist.

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Natalie Mason