Conference Coverage

PLA testing brings nuance to the diagnosis of early-stage melanoma



– Although skin biopsy remains the gold standard for diagnosing early-stage melanoma, advances in genetic expression profiling are helping dermatologists provide a nuanced approach to managing suspicious lesions.

One such test, the Pigmented Lesional Assay (PLA) uses adhesive patches applied to lesions of concern at the bedside to extract RNA from the stratum corneum to help determine the risk for melanoma.

Director of Melanoma and Pigmented Lesion Clinics at Newton Wellesley Dermatology and Tufts Medical Center

Dr. Caroline C. Kim

At the annual meeting of the American Academy of Dermatology, Caroline C. Kim, MD, director of melanoma and pigmented lesion clinics at Newton Wellesley Dermatology, Wellesley Hills, Mass., and Tufts Medical Center, Boston, spoke about the PLA, which uses genetic expression profiling to measure the expression level of specific genes that are associated with melanoma: PRAME (preferentially expressed antigen in melanoma) and LINC00518 (LINC). There are four possible results of the test: Aberrant expression of both LINC and PRAME (high risk); aberrant expression of a single gene (moderate risk); aberrant expression of neither gene (low risk); or inconclusive.

Validation data have shown a sensitivity of 91% and a specificity of 69% for the PLA, with a 99% negative predictive value; so a lesion that tested negative by PLA has a less than 1% chance of being melanoma. In addition, a study published in 2020 found that the addition of TERT (telomerase reverse transcriptase) mutation analyses increased the sensitivity of the PLA to 97%.

While the high negative predictive value is helpful to consider in clinical scenarios to rule-out melanoma for borderline lesions, one must consider the positive predictive value as well and how this may impact clinical care, Dr. Kim said. In a study examining outcomes of 381 lesions, 51 were PLA positive (single or double) and were biopsied, of which 19 (37%) revealed a melanoma diagnosis. In a large U.S. registry study of 3,418 lesions, 324 lesions that were PLA double positive were biopsied, with 18.7% revealing a melanoma diagnosis.

“No test is perfect, and this applies to PLA, even if you get a double-positive or double-negative test result,” Dr. Kim said. “You want to make sure that patients are aware of false positives and negatives. However, PLA could be an additional piece of data to inform your decision to proceed with biopsy on select borderline suspicious pigmented lesions. More studies are needed to better understand the approach to single- and double-positive PLA results.”

The PLA kit contains adhesive patches and supplies and a FedEx envelope for return to DermTech, the test’s manufacturer, for processing. The patches can be applied to lesions at least 4 mm in diameter; multiple kits are recommended for those greater than 16 mm in diameter. The test is not validated for lesions located on mucous membranes, palms, soles, nails, or on ulcerated or bleeding lesions, nor for those that have been previously biopsied. It is also not validated for use in pediatric patients or in those with skin types IV or higher. Results are returned in 2-3 days. If insurance does not cover the test, the cost to the patient is approximately $50 per lesion or a maximum of $150, according to Dr. Kim.


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