Dermoscopy increases the sensitivity for skin cancer detection, decreases the number of benign lesions biopsied for each malignant diagnosis, and enables the diagnosis of thinner melanomas compared with naked eye examination. Multiple meta-analyses have identified that dermoscopy improves the diagnostic accuracy for melanoma when compared with naked eye examination. In addition, studies have established that dermoscopy can aid in the detection of keratinocyte carcinomas. Dermoscopy triage algorithms have been developed to help novices decide when a biopsy or a referral is most appropriate. In this article, the authors illustrate the dermoscopic features that assist in identifying melanoma and keratinocyte carcinomas.
Key points
- •
Dermoscopy increases diagnostic accuracy and sensitivity for melanoma, and helps in the detection of thinner tumors.
- •
Multiple studies have established that dermoscopy is an aid for diagnosing basal cell carcinoma; the presence of dermoscopic criteria can predict the histopathological subtype of basal cell carcinoma.
- •
Although actinic keratosis, Bowen disease/squamous cell carcinoma in situ, invasive squamous cell carcinoma, and keratoacanthoma share common dermoscopic features, specific criteria can permit diagnostic discrimination.
- •
Dermoscopy novices can benefit from using diagnostic or triage algorithms to improve their diagnostic abilities and management decisions.
Introduction
Dermoscopy has been shown to increase sensitivity for skin cancer detection, decrease the benign-to-malignant biopsy ratio, and allow for the diagnosis of thinner melanomas compared with naked eye examination (NEE). In 2009, a survey of academic dermatologists and chief residents in US dermatology training programs demonstrated that 84% of attending dermatologists used dermoscopy in daily practice and 90.2% of chief dermatology residents received dermoscopy training as part of their curricula. These findings represented a significant increase in training and use of dermoscopy compared with a similar survey performed 10 years before. The use of dermoscopy has also increased among nondermatologist physicians who actively participate in skin cancer management, such as family physicians.
Despite the growing number of practitioners incorporating dermoscopy into their daily practices, there remain significant barriers, such as lack of training resources, preventing its widespread adoption. Dermoscopic teaching methodologies, which include pattern analysis, diagnostic algorithms, and simplified triage algorithms, continue to emerge. They aim to provide an entry point in educating beginners in dermoscopy. Here, the authors review the diagnostic utility of dermoscopy for detection of melanoma and keratinocyte carcinomas (KC; also known as nonmelanoma skin cancers) and outline the specific dermoscopic features that can help discriminate these cancers from benign lesions. A review of dermoscopic teaching methodologies, including triage algorithms, is also provided.
Introduction
Dermoscopy has been shown to increase sensitivity for skin cancer detection, decrease the benign-to-malignant biopsy ratio, and allow for the diagnosis of thinner melanomas compared with naked eye examination (NEE). In 2009, a survey of academic dermatologists and chief residents in US dermatology training programs demonstrated that 84% of attending dermatologists used dermoscopy in daily practice and 90.2% of chief dermatology residents received dermoscopy training as part of their curricula. These findings represented a significant increase in training and use of dermoscopy compared with a similar survey performed 10 years before. The use of dermoscopy has also increased among nondermatologist physicians who actively participate in skin cancer management, such as family physicians.
Despite the growing number of practitioners incorporating dermoscopy into their daily practices, there remain significant barriers, such as lack of training resources, preventing its widespread adoption. Dermoscopic teaching methodologies, which include pattern analysis, diagnostic algorithms, and simplified triage algorithms, continue to emerge. They aim to provide an entry point in educating beginners in dermoscopy. Here, the authors review the diagnostic utility of dermoscopy for detection of melanoma and keratinocyte carcinomas (KC; also known as nonmelanoma skin cancers) and outline the specific dermoscopic features that can help discriminate these cancers from benign lesions. A review of dermoscopic teaching methodologies, including triage algorithms, is also provided.
Dermoscopy for the diagnosis and management of cutaneous melanoma
In 2001, the first meta-analysis of the diagnostic power of dermoscopy found dermoscopy to be more accurate than NEE alone for the diagnosis of cutaneous melanoma. Two additional meta-analyses have since reinforced these findings. The most recent, by Vestergaard and colleagues, included only prospective studies performed in a clinical setting and thus more accurately reflected everyday dermoscopy use. In total, 8487 suspicious pigmented and nonpigmented lesions were included, and melanoma prevalence ranged from 0.5% to 21.1% with a Breslow thickness that ranged from 0.35 to 0.95 mm. Dermoscopic and clinical accuracy were evaluated through the diagnostic odds ratio (DOR), which considers both sensitivity and specificity and their respective tradeoffs. The DOR for dermoscopy was 15.6 (confidence interval [CI]: 2.9–83.7, P = .016) times higher for dermoscopy than NEE. A summary estimate of sensitivity was higher with dermoscopy (0.90, CI: 0.80–0.95) than for NEE (0.71, CI: 0.59–82, P = .002) ; although specificity was higher for dermoscopy (0.90, CI: 0.57–98) than NEE (0.81, CI: 0.48–0.95, P = .18), it was not statistically significant.
In all 3 meta-analyses, diagnostic accuracy was dependent upon the experience of the examiner. However, inexperienced users, after a 2-hour course, had an improved sensitivity without compromising their specificity. Terushkin and colleagues found, through assessment of the benign-to-malignant biopsy ratio (BMR), that a single dermatologist newly adopting dermoscopy experienced a learning curve. Initially, the BMR of the dermatologist increased compared with NEE, but with time and experience, the BMR dropped below the baseline value with NEE alone and approached the level of pigmented lesion specialists. Several studies have demonstrated that short training modules can improve the diagnostic performance of inexperienced dermatologists, general practitioners, and even medical students. However, the training modalities have varied widely among studies, and the ideal teaching method for beginners remains to be standardized.
The BMR (which is directly related to positive predictive value), although not a surrogate, is impacted by the sensitivity and specificity of dermoscopy. Improvements in this ratio suggest that the increased sensitivity seen with dermoscopy does not entail an increase in the number of unnecessary biopsies and thus an increase in morbidity. Carli and colleagues retrospectively examined 2 users before and after the introduction of dermoscopy and 4 nonusers. Analysis demonstrated a significant improvement in the BMR over a 4-year study period in the dermoscopy arm (18:1–4.3:1, P = .037). The BMR for nonusers had no significant difference at the beginning and the end of the study (11.8:1–14.8:1). In a randomized controlled trial comparing one-time evaluations of equivocal pigmented lesions with dermoscopy or NEE, 9% of patients followed with dermoscopy were referred for biopsy or excision compared with 15.6% with NEE ( P = .013). The reduction in surgical morbidity was not hindered by a decreased ability to diagnose melanoma. Finally, a multicenter survey over 10 years showed that the BMR at sites dedicated to skin cancer treatment improved from 12.8 to 6.8 ( P <.001) and remained unchanged in sites not dedicated to screening for skin cancer. The investigators of that study argue that the introduction of dermoscopy was largely responsible for the observed improvement in the BMR.
Dermoscopy and dermoscopic screening allow for the earlier detection of melanoma and improved clinical management. Several studies have shown that dermoscopic monitoring of lesions enables the detection of thin, featureless melanomas. In a meta-analysis with a mean follow-up of 30 months, Salerni and colleagues showed dermoscopy users to detect a greater number of thinner melanomas compared with NEE (mean Breslow depth 0.77 mm vs 1.43 mm, P <.05). Haenssle and colleagues found that participation in specialized dermoscopic screening programs and dermoscopic examinations at the time of diagnosis were also significantly associated with thinner melanomas ( P <.01). Dermoscopy users have identified melanoma-specific dermoscopic features that have enabled them to recognize melanoma with the sensitivity and specificity described. The following sections expand upon these melanoma-specific dermoscopic features and other features for basal cell carcinoma (BCC) and keratinizing carcinomas.
Dermoscopic features in melanoma
By allowing for the in vivo assessment of subsurface skin structures, dermoscopy offers a window into the histologic diagnosis of skin cancers. Many of the described dermoscopic features have known histologic correlates. The presence of these features can provide insight into the cellular nature of skin neoplasms and allow for more precise clinical diagnoses. When the dermoscopic diagnosis is unclear, structures can hint at malignant potential. Although the dermoscopic features discussed in Table 1 can be applied to any lesion on the skin, there are additional criteria in Table 2 that are specific to lesions on the face, mucosa, nails, and volar surfaces, which are outlined in later discussion. Examples of dermoscopic features found in melanoma are shown in Fig. 1 .
Lentigo maligna and lentigo maligna melanoma both arise on sun-damaged skin, most commonly the face and scalp (both lentigo maligna and lentigo maligna melanoma are represented by the abbreviation LMM). The anatomic predilection for the face and sun-damaged skin entails a broad differential diagnosis, including pigmented actinic keratosis (AK), lichen planus-like keratoses, and early-flat seborrheic keratoses. Dermoscopy can help the user sort through the numerous diagnoses. Facial skin has a flattened dermoepidermal junction resulting in absence of traditional reticular patterns commonly seen in melanocytic lesions. Instead, the pigmentation is punctuated by adnexal structures, creating a pseudonetwork. LMM-specific structures include asymmetrical pigmentation of follicular openings, dots aggregated around adnexal openings, polygonal lines and rhomboid structures, and dark blotches with or without obliteration of the adnexal openings ( Fig. 2 A ).
Additional dermoscopic features are also needed to evaluate for melanoma arising on the nail apparatus, mucosa, or volar skin. In melanoma of the nail apparatus, dermoscopy of the pigmented band will show multiple brown to black lines with irregular arrangement and thickness and possible areas of pigment interruption (see Fig. 2 B). The mucosa comprises a wide range of anatomic sites, such as the lip, glans penis, anogenital orifice, labia, and praeputium. On dermoscopy, an early sign of mucosal melanoma is the presence of structureless areas and gray color. More advanced melanoma can present with multiple patterns and colors, particularly white, blue, and/or gray (see Fig. 2 C). The dermoscopic appearance of acral lentiginous melanoma (ALM) is shaped by the unique furrow and ridge pattern of acral volar skin surfaces. Melanocytic features specific to ALM are the parallel ridge pattern and irregular diffuse pigmentation (see Fig. 2 D). Tables 1 and 2 provide an overview of melanoma-specific criteria, including definitions, pictorial examples, and reported sensitivities, specificities, and odds ratios. This list was compiled using the most recent definitions of dermoscopic criteria published by the International Dermoscopy Society in 2016.
Dermoscopy for the diagnosis and management of keratinocyte carcinomas
In addition to differentiating nevi from melanoma and detecting early melanoma, dermoscopy can also be used to detect KC. Rosendahl and colleagues examined 217 consecutive pigmented nonmelanocytic lesions, of which 138 were malignant, with both dermoscopy and NEE. They reported a diagnostic improvement with dermoscopy of 0.89 (area under the receiver operating curve) compared with 0.83 with NEE alone ( P <.001). In a 2016, 2-part study of optional then mandatory dermoscopy use, the overall diagnostic sensitivity of BCC was 93.3% (91.9–94.5) and specificity was 91.8% (90.6–93.0). Furthermore, dermoscopy when compared with NEE was shown to help predict BCC histopathology subtypes. In the following sections, the specific diagnostic features of KC are detailed further.
Dermoscopic features in basal cell carcinoma
BCCs are broadly classified as pigmented or nonpigmented. Although most BCCs on NEE are nonpigmented, 29.8% of these lesions actually reveal pigment structures when viewed with dermoscopy. The pigmented structures seen in BCC include blue-gray globules or ovoid nests, spoke-wheel structures, and leaflike areas. The structures seen in nonpigmented or pigmented BCC include arborizing vessels, shiny white blotches and strands (seen with polarized dermoscopy), and ulcers/erosions ( Table 3 ). Studies have demonstrated that certain dermoscopic structures and patterns are associated with different subtypes of BCC. The presence of spoke-wheel and leaflike structures, multiple small erosions, short fine vessels, and shiny white blotches and strands in a nonpalpable lesion is associated with superficial BCC. In contrast, the presence of blue-gray globules, ovoid nest, arborizing vessels, and ulceration is associated with nodular BCC. Examples of dermoscopic features found in BCC are shown in Fig. 3 .
Dermoscopic features in actinic keratoses, squamous cell carcinoma in situ/Bowen disease, invasive squamous cell carcinoma, and keratoacanthoma
Dermoscopic features have been identified that can assist in diagnosing AK, Bowen disease (BD), or in situ squamous cell carcinoma (full-thickness atypia/intraepidermal carcinoma), invasive squamous cell carcinoma (SCC), and keratoacanthoma (KA). Dermoscopically, these lesions exist on a spectrum that the authors have grouped under the category of keratinizing skin cancer (KSC); thus, several features, such as scale, vascular structures, and erythema, are ubiquitous among them. Although more research is needed to determine the sensitivity and specificity of these features, it appears the authors can usually differentiate the full spectrum of KSCs from AKs to IECs to SCCs.
There are several notes that need to be made concerning the data presented in Tables 4–6 . Many of the lesions examined occur in higher frequency on the head and neck area, thus making generalizability to KSCs on other body parts difficult. In addition, several studies look at specific comparisons of the dermoscopic features of AK, for example, to those of SCC, but not all possible diagnoses. When a definition was absent from the International Society of Dermoscopy 2016 consensus meeting, the authors cited definitions provided from other sources. Finally, although purported to be significant, some features have yet to be rigorously studied to determine their diagnostic significance. Tables 4–6 represents the authors’ best representation of available data and, it is hoped, makes clear when little analytical information is known. In addition, examples of dermoscopic features found in KSC are shown in Fig. 4 .
Related posts:
Clinical Diagnosis of Skin Cancer
Temporal Image Comparison (Serial Imaging) in Assessing Pigmented Lesions
Using Raman Spectroscopy to Detect and Diagnose Skin Cancer In Vivo
Proteomic Mass Spectrometry Imaging for Skin Cancer Diagnosis
Smartphone-Based Applications for Skin Monitoring and Melanoma Detection
Teledermatology Applications in Skin Cancer Diagnosis
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
