The detection of melanoma can be challenging. Many patients have clinically equivocal lesions in cosmetically sensitive areas or have multiple suspicious lesions. Epidermal genetic information retrieval is a noninvasive diagnostic method involving the application of adhesive tape onto the skin’s surface to recover genomic material from the epidermis. This genomic material can then be used in assays to determine gene expression profiles. Studies have shown the potential of this technology to aid clinicians in differentiating between melanomas and nevi. Although this technology is not meant to replace a biopsy, it can help guide the decision whether to biopsy.
Key points
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Epidermal genetic information retrieval (EGIR) is a noninvasive diagnostic method involving the application of adhesive tape onto the skin’s surface to recover genomic material from the epidermis.
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Preliminary studies have shown the potential of this technology to aid clinicians in differentiating between melanomas and nevi.
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Although not meant to replace a biopsy, EGIR by adhesive patch sampling can guide the decision on surgical biopsy in patients who may have numerous nevi or in those with a suspect lesion on a cosmetically sensitive area.
Introduction
It is widely accepted that the early detection of melanoma improves survival. In order to properly evaluate a lesion concerning for melanoma, an excisional biopsy is typically performed. For some patients, such as those with a questionable lesion in a cosmetically sensitive area or patients with numerous atypical melanocytic nevi, the risk of morbidity associated with such a procedure should be carefully weighed against the likelihood that the lesion in question is malignant. Although dermoscopy has improved the accuracy of melanoma diagnosis, its utility is highly user dependent; even for pigmented lesions specialists, the number of benign lesions biopsied for every melanoma detected ranges from 5 to 1 at best to 15 to 1.
Advances in technology have led to improved noninvasive diagnostic modalities for melanoma. However, for many of these approaches, advanced training is required and application is user dependent. A more objective noninvasive test with high sensitivity and specificity that could minimize interuser variability would be highly beneficial for improving diagnosis of melanoma and for reducing the number of unnecessary skin biopsies.
In recent years, a new method was introduced as an alternative to the aforementioned technologies. Adhesive patch skin surface sampling, also known as epidermal genetic information retrieval (EGIR) (DermTech International, Inc, La Jolla, CA) is distinct in its analysis of genomic material from the lesion in question using noninvasive methods. EGIR is the focus of the present article.
Introduction
It is widely accepted that the early detection of melanoma improves survival. In order to properly evaluate a lesion concerning for melanoma, an excisional biopsy is typically performed. For some patients, such as those with a questionable lesion in a cosmetically sensitive area or patients with numerous atypical melanocytic nevi, the risk of morbidity associated with such a procedure should be carefully weighed against the likelihood that the lesion in question is malignant. Although dermoscopy has improved the accuracy of melanoma diagnosis, its utility is highly user dependent; even for pigmented lesions specialists, the number of benign lesions biopsied for every melanoma detected ranges from 5 to 1 at best to 15 to 1.
Advances in technology have led to improved noninvasive diagnostic modalities for melanoma. However, for many of these approaches, advanced training is required and application is user dependent. A more objective noninvasive test with high sensitivity and specificity that could minimize interuser variability would be highly beneficial for improving diagnosis of melanoma and for reducing the number of unnecessary skin biopsies.
In recent years, a new method was introduced as an alternative to the aforementioned technologies. Adhesive patch skin surface sampling, also known as epidermal genetic information retrieval (EGIR) (DermTech International, Inc, La Jolla, CA) is distinct in its analysis of genomic material from the lesion in question using noninvasive methods. EGIR is the focus of the present article.
Epidermal genetic information retrieval
EGIR involves obtaining and analyzing RNA from epidermal cells for the expression of genes associated with melanoma. The exact mechanism of how RNA originating from melanocytes is found in the superficial epidermis and is thus detected by EGIR is not yet known. Some investigators hypothesize that this may be because of shedding of melanocytes toward the superficial epidermis, or pagetoid spread of melanocytes, or exchange of subcellular material between the melanocytes and keratinocytes.
EGIR was first developed for the study of other dermatologic conditions. It has been used to differentiate allergic from irritant contact dermatitis and to analyze the expression of specific cytokines in psoriatic plaques by quantitative reverse transcription polymerase chain reaction (RT-PCR) assay. Wong and colleagues later found that RNA obtained via adhesive patch sampling was suitable for use in DNA microarray experiments and that it relayed information from epidermal cells located below the stratum corneum. This finding was the basis for adhesive patch sampling of melanocytic lesions for a diagnostic purpose. In order to investigate whether the adhesive patch sampling could distinguish a melanoma from a nevus, an adhesive tape was applied to the surface of the lesion to retrieve epidermal cells, from which RNA was extracted using RT-PCR. This RNA was then hybridized to a DNA microarray chip consisting of numerous genes to determine the gene expression profile of the lesion.
The preliminary investigation by Wachsman and colleagues was designed to compare the gene expression profiles of melanoma and benign nevi. The investigators performed EGIR by applying 4 adhesive tape disks onto pigmented lesions ( Fig. 1 ), followed by surgical removal of the lesions for histopathologic analysis by 2 independent dermatopathologists. In total, 20 melanomas (9 in situ and 11 invasive), 62 nevi, and 17 nonlesional normal skin samples were included in the study. Lesions suspicious for melanoma that were bleeding or ulcerated were excluded. RNA from the 4 disks was pooled and amplified using quantitative RT-PCR and profiled for gene expression on a gene chip containing 47,000 transcripts. By this method, differential expression levels among melanomas, nevi, and normal skin of 317 genes were identified; of these, 89 genes were shown to be differentially expressed between melanomas and nevi. These results showed that EGIR has potential for being used to distinguish melanomas from nevi.
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