What is dermatoscopy (skin surface microscopy) and how is it used for early detection of skin cancers in high-risk individuals, such as those with fair skin, significant sun exposure, or a family history of skin cancer?

Dermatoscopy: A Comprehensive Overview

What is Dermatoscopy?

Dermatoscopy (also called epiluminescence microscopy or skin surface microscopy) is a non-invasive handheld illuminated magnifier that allows detailed examination of the skin down to the level of the superficial dermis, significantly enhancing the detection of both melanoma and non-melanoma skin cancers compared to naked-eye visual inspection alone. 1

• Dermoscopy is a precision-built tool that has become integral to clinical skin examination, markedly improving early detection of melanocytic and non-melanocytic skin cancers. 2
• The technique allows visualization of subsurface skin structures not visible to the naked eye, enabling more accurate differentiation between benign and malignant lesions. 3

Diagnostic Accuracy and Clinical Impact

For Melanoma Detection

• Dermoscopy by an experienced physician enhances diagnostic accuracy for melanoma detection. 4
• Multiple meta-analyses confirm that dermoscopy improves diagnostic accuracy for melanoma compared with naked-eye examination alone. 5
• Dermoscopy increases sensitivity for skin cancer detection, decreases the number of benign lesions biopsied for each malignant diagnosis, and enables diagnosis of thinner melanomas. 5
• The technique helps clinicians differentiate benign from malignant lesions through the presence or absence of specific dermoscopic structures that have direct histopathologic correlates. 3

For Non-Melanoma Skin Cancers

• For basal cell carcinoma (BCC) detection, dermoscopy performed in-person is significantly more accurate than visual inspection alone, with a relative diagnostic odds ratio of 8.2. 1
• At a fixed specificity of 80%, dermoscopy demonstrates 14% higher sensitivity (93% versus 79%) compared to visual inspection alone for BCC detection. 1
• At a fixed sensitivity of 80%, dermoscopy shows 22% higher specificity (99% versus 77%) compared to visual inspection for BCC. 1
• In practical terms: among 1000 lesions with 170 BCCs, dermoscopy would result in 24 fewer missed BCCs or 183 fewer unnecessary excisions compared to visual inspection alone. 1

Clinical Applications Beyond Diagnosis

Therapeutic Planning and Monitoring

• Dermoscopy is increasingly important for selecting appropriate therapies and assessing treatment response for non-melanoma skin cancers, including basal cell carcinoma, actinic keratoses, and squamous cell carcinoma. 2
• The technique serves as a valid tool for preoperative assessment of tumor margins in basal cell carcinoma. 2
• Dermoscopy enables follow-up monitoring of actinic keratoses after topical treatment. 2

Histopathologic Correlation

• Dermoscopic structures have direct histopathologic correlates, allowing prediction of certain histologic findings in skin cancers. 3
• Ex vivo dermoscopy on excised specimens can improve histologic diagnostic accuracy through targeted step-sectioning in areas of concern. 3
• Dermoscopy can help select tumor areas with genetic importance, as some dermoscopic features correlate with mutations having therapeutic relevance. 3

Diagnostic Criteria and Methodology

The ABCDE Rule

Clinical visual skin examination, enhanced by dermoscopy, assesses lesions using the "ABCDE rule" to identify suspicious characteristics: 4

• Asymmetry: Irregular shapes or halves that don't match 6
• Border irregularity: Jagged, notched, or blurred edges 6
• Color heterogeneity: Multiple colors or uneven color distribution 6
• Diameter: Lesions greater than 6 mm (though many primary melanomas today have diameter <5 mm) 4, 6
• Evolution: Recent changes in size, color, elevation, or other characteristics 4, 6

The "Ugly Duckling" Concept

• The "ugly duckling" sign identifies moles that look different from surrounding moles on the same patient. 4, 6
• This concept is particularly useful for detecting suspicious pigmented lesions that stand out from the patient's baseline nevus pattern. 4

Who Should Use Dermatoscopy?

Training and Expertise Requirements

• Dermatoscopy for early melanoma diagnosis should only be used by those familiar with the technique, as its accuracy depends on the experience of the dermatologist. 4
• The technique cannot currently be recommended as a routine tool for untrained clinicians. 4
• Patient-operated diagnostic devices without medical supervision are presently not recommended. 4

Clinical Settings

• Dermoscopy is increasingly used in both specialist and primary-care settings. 1
• The technique is particularly valuable in secondary-care (referred) populations and for evaluating pigmented lesions or mixed lesion types. 1

High-Risk Populations Requiring Enhanced Surveillance

Constitutional Risk Factors

Individuals at higher risk for skin cancer who benefit most from dermoscopic evaluation include those with: 4

• Fair complexion, red or blond hair, and light-colored eyes 7
• Multiple (≥100) nevi 4
• Dysplastic nevus (atypical mole) 4
• Giant congenital nevi 4
• Family history of melanoma (first-degree relative) 4, 8
• Familial atypical mole and melanoma syndrome 4, 8
• Personal history of previous skin cancer 4

Behavioral and Environmental Risk Factors

• History of sunburns, particularly during childhood 7
• Significant sun exposure or use of indoor tanning beds 4
• History of therapeutic radiation 7
• Immunosuppression 7

Surveillance Recommendations for High-Risk Patients

• High-risk patients should be referred to a dermatologist for monitoring and screening examinations at any age. 8
• Automated videodermoscopy systems can provide improved diagnostic accuracy for patients with multiple atypical nevi during follow-up. 4
• Full body imaging with high-resolution pictures has shown improvement in early detection. 4

Screening Recommendations for Average-Risk Populations

Evidence Limitations

• The USPSTF concludes that current evidence is insufficient to assess the balance of benefits and harms of visual skin examination by a clinician to screen for skin cancer in asymptomatic adults (Grade I statement). 4
• Evidence is inadequate to reliably conclude that early detection of skin cancer through visual examination leads to improved outcomes. 4
• The Canadian Task Force on Preventive Health Care similarly found insufficient evidence to recommend for or against routine screening in the general population. 4, 8

Age-Based Recommendations from Other Organizations

Despite insufficient evidence from USPSTF, other organizations provide the following guidance:

• The American Cancer Society recommends cancer-related checkup including skin examination every 3 years for ages 20-40, and annually for age 40 and older. 8
• Monthly self-examinations are recommended for all adults. 8
• Complete skin examinations detect melanoma 6.4 times more frequently than partial examinations. 8

Moderately Increased Risk Patients

• The American Medical Association recommends annual skin examinations by a primary care physician for patients at moderately increased risk. 8
• These patients should discuss screening frequency with their physician and perform monthly self-examinations. 8

Important Clinical Considerations and Pitfalls

Potential Harms of Screening

• Potential harms include misdiagnosis, overdiagnosis, and resulting cosmetic or functional adverse effects from biopsy and overtreatment. 4
• The majority of suspicious skin lesions excised during screening are not cancerous, leading to false-positive results and unnecessary biopsies. 4
• Some detected lesions (thin melanomas, non-melanoma skin cancers) may have little potential for malignant spread, potentially resulting in overtreatment. 4

Special Populations

• Melanomas can occur in non-sun-exposed areas, particularly in people with darker skin, who are often diagnosed at later stages when skin cancer is more difficult to treat. 8, 6
• This represents a critical health disparity requiring heightened clinical awareness. 8, 6

Diagnostic Biopsy Technique

• The standard practice for suspected melanocytic lesions is complete excisional biopsy with a narrow (2 mm) rim of normal skin under local anesthetic, rather than partial biopsy. 4
• Excisional biopsy is preferred because: partial examination risks misdiagnosis, entire lesion examination is necessary to assess all histological parameters (especially maximum thickness), and tissue destruction from other methods compromises final diagnosis. 4
• Frozen sections should be discouraged; scalpel excision is preferred over laser or electro-coagulation. 4

Algorithm and Checklist Limitations

• There is insufficient evidence supporting the use of currently-available formal algorithms to assist dermoscopy diagnosis for BCC. 1
• While machine-learning algorithms trained on dermoscopic images show promise with diagnostic accuracy comparable to board-certified dermatologists, their use in clinical practice remains to be evaluated. 4

Epidemiologic Context

Melanoma Statistics

• In 2016, an estimated 76,400 U.S. adults developed melanoma and 10,100 died from the disease. 4
• Melanoma represents about 1% of skin cancers but causes more deaths than basal cell and squamous cell carcinomas combined. 7
• The 5-year survival rate varies dramatically by stage: 99.5% for localized disease versus 31.9% for metastatic disease. 7
• Melanoma incidence has more than doubled since 1973, increasing from 5.7 to 14.3 cases per 100,000 people by 1998. 7

Non-Melanoma Skin Cancer

• Basal cell and squamous cell carcinomas represent over 98% of all skin cancer cases. 4, 7
• Non-melanoma skin cancer rarely results in death or substantial morbidity (<0.1% of patient deaths). 4, 7
• Basal cell carcinoma is the most common cancer in the United States, with approximately 2 million new cases annually. 7