Overview

Dermoscopy is a non-invasive diagnostic technique performed using a handheld instrument called a dermatoscope. A dermatoscope is typically equipped with a magnifying lens (usually X10) and a light source. It allows for the inspection of subsurface structures that are generally not visible to the naked eye, including those in the epidermis, the dermoepidermal junction, and the papillary dermis. It works by reduction of skin surface light reflection by non polarized light contact with immersion fluids (water, alcohols, oil, gels) or by using polarized light contact or noncontact. Polarized light dermoscopy makes deeper structures, such as blood vessels and shiny white structures, more conspicuous, while non-polarized light is better for visualizing superficial epidermal structures such as milia-like cysts and comedo-like openings in seborrheic keratoses. Both types of light provide complementary information.

Some examples of handheld dermatoscopes that are currently on the market: Dermlite DL5, Heine Delta 30, CAZIO DZ-D100: DERMOCAMERA.

Colors and structures

Dermoscopy reveals various colors including yellow, red, brown, blue, gray, black, and white. The structures seen are influenced by the distribution and amount of melanin, keratin, collagen, and vascularity. Melanin appears as different colors at different depths in the skin (Figure 1). A histologic correlation has been established for most of the structures seen with dermoscopy. The dermoscopic diagnosis of skin lesions involves the recognition of the presence or absence of specific structures to confirm or rule out a given diagnosis.

Figure 1. Different colors at different depths in the skin.

Diagnostic Approaches

Metaphoric vas Analytic approach

1. Metaphoric approach (Top-Down) : Observers recognize the general context, generate a hypothesis for the likely diagnosis, and then perform a targeted search for features to confirm or refute this hypothesis. this approach uses metaphoric terms to describe dermoscopic structures, meaning it denotes a structure based on a perceived visual similarity to an unrelated object. (Figure 2).

2. Analytic Approach (Bottom-Up): Observers search for individual features to arrive at a diagnosis. Kittler proposed descriptive terms based on five basic geometric elements: lines, circles, clods, and dots (Figure 3). A set of dermoscopic structures in combination of colors and clues constitutes clues for specific diagnoses.

In recent years, the vocabulary of dermoscopy has expanded so significantly that even experts find it challenging to manage the multitude of terms. In 2016, an expert panel proposed a standardized dictionary, incorporating both metaphoric and descriptive terms, to promote consistent use of dermoscopic terminology (4). However, in real-life clinical and research settings, the lack of standardization continues to be a problem, and solutions are still being sought.

Figure 2. Various dermoscopic structures for melanoma, metaphoric approach. Dermoscopedia.

Figure 3. Analytic Approach. Dermoscopy, pattern analysis 2nd edition Harald Kittler.

Algorithms

1. Pattern Analysis: This method boasts superior specificity compared to other quantitative scoring systems and is favored by most experienced clinicians. Observers search for individual features to arrive at a diagnosis, classifying lesions as either melanocytic (nevi vs. melanoma) or non-melanocytic. However, some lesions may display features resembling melanocytic structures, while melanomas may lack these structures.

2. Revised Pattern Analysis: In the new approach, the observer is required to make a specific diagnosis by recognizing patterns associated with common, benign neoplasms. If an unequivocal diagnosis of one of the benign lesions cannot be made with confidence, the observer will proceed to step 2, where they will determine if the overall pattern of the lesion (i.e., distribution of colors and structures) is organized or disorganized. Lesions with a disorganized pattern are more likely to be malignant, and based on the presence of specific structures

3. Quantitative Methods: Novices may benefit from simpler, more reproducible methods such as the ABCD rule, the Menzies method, and the seven-point checklist.

Role of Dermoscopy in Skin Cancer Detection

The decision to biopsy a lesion should be based on a combination of both clinical and dermoscopic examination of the lesion, as well as surrounding areas, change history, associated symptoms, skin type, location, and personal or family history of skin cancers

Dermoscopy significantly enhances both the sensitivity and specificity of skin tumors detection compared to visual examination alone. Meta-analyses suggest that dermoscopy improves the sensitivity of melanoma detection to around 85-90%, compared to 60-70% with naked-eye examination alone (5).

In patients with dysplastic nevus syndrome, identifying the "signature nevus" pattern and spotting "ugly duckling" lesions are useful strategies. For macular (non-palpable) suspected lesions short-term dermoscopic monitoring, which involves comparing digital images of the same lesion taken 3-6 months apart, is also appropriate.

If a lesion is considered benign, the patient should be reassured, educated on skin self-examination, and instructed to return if any changes occur. Lesions with dermoscopic features suggestive of melanoma or other skin cancers should be excised and sent for histopathologic examination.

Dermoscopy in general dermatology

Traditionally, dermoscopy has been used primarily to diagnose skin tumors and differentiate between benign and malignant melanocytic lesions. However, its application has extended significantly beyond this. In recent years, dermoscopy has proven to be a valuable tool for the noninvasive diagnosis of various dermatological disorders. This includes the examination of scalp and hair diseases (trichoscopy), nail and nailfold abnormalities (onychoscopy), cutaneous infections and infestations (entomodermoscopy), and inflammatory dermatoses (inflammoscopy).

The most important criteria to consider when using dermoscopy in general dermatology are: (1) the morphology and arrangement of vascular structures, (2) scaling patterns, (3) colors, (4) follicular abnormalities, and (5) specific features or clues. Dermoscopic findings must be interpreted within the overall clinical context of the patient, including personal and family history, number, location, morphology, and distribution of the lesions.

Dermoscopy courses:

(1). Online HealthCert Certificate and Professional Diploma Program in Dermoscopy

https://www.healthcert.com/certificate-diploma-courses-in-dermoscopy

(2) IDS eLearning short courses for dermoscopists.

https://www.dermoscopy-ids-courses.com/

(3). ISCD International Short Course on Dermoscopy Graz

https://www.medunigraz.at/iscd

4. Dermoscopy Excellence – Digital Training https://www.dermoscopyexcellence.org/digital-training/

References:

(1). https://pubmed.ncbi.nlm.nih.gov/27613297/

(2). https://jamanetwork.com/journals/jamadermatology/fullarticle/2782522

(3). https://pubmed.ncbi.nlm.nih.gov/25370214/

(4). https://pubmed.ncbi.nlm.nih.gov/21175563/