Dermoscopy

Dermoscopy is non-invasive epiluminescence microscopy at about 10 times magnification. It reveals pigment patterns and vascular structures beneath the skin surface that are not visible to the naked eye.

It is used for pigmented and non-pigmented skin lesions, especially to assess melanoma. In trained hands, it improves diagnostic accuracy over naked eye examination. Dermoscopy supports clinical decisions but does not replace histological diagnosis.

Polarised and non-polarised light show different features. Contact dermoscopy requires a fluid medium, while non-contact dermoscopy uses polarised light without fluid.

Methods. The most common scoring methods are pattern analysis, the 7-point checklist and the Menzies method. One method is applied consistently within a service.

Interpretation.

• Major criteria each score 2 points: atypical pigment network, blue white veil, and atypical vascular pattern.
• Minor criteria each score 1 point: irregular streaks, irregular blotches, irregular dots or globules, and regression structures.
• A total of 3 or more on the 7-point checklist suggests melanoma and warrants biopsy or excision referral.
• Arborising vessels and leaf like areas suggest basal cell carcinoma. Glomerular or hairpin vessels suggest squamous cell carcinoma. Milia like cysts and comedo like openings suggest seborrhoeic keratosis.
• Palms, soles and nails show a parallel ridge pattern, which is more concerning when irregular.

Critical values and findings needing immediate action.

• A 7-point score of 3 or more in a lesion with irregular features requires prompt referral for histology.
• Rapid change in a lesion over serial dermoscopy requires urgent review.

Limitations and artefacts. Sun damage, inflammation and hair can obscure features. Amelanotic melanoma may lack pigment entirely, and dermoscopy can miss it. Most lesions examined are benign, so a positive finding has a lower predictive value in primary care than in specialist settings.

Follow up tests. Histology confirms suspicious lesions. Stable lesions are monitored with serial dermoscopic images to detect change over time.

Special groups. Children may show Spitz naevi, which can mimic melanoma and require specialist review. Dermoscopy is not contraindicated in pregnancy. Patients with darker skin may have acral or mucosal lesions where pattern interpretation differs.