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← Dermatology indexChapter sections
Purpose and principlesIndications, selection and cautionsMethod and interpretationClinical next stepsRisks, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Dermatoscopy principles

Dermatology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Time-critical presentation

Escalate urgently when assessment for Dermatoscopy principles reveals systemic toxicity, airway or eye involvement, extensive skin failure, a non-blanching eruption in an unwell patient, or a rapidly changing lesion suspicious for aggressive malignancy.

Purpose and principles

Use dermatoscopy as an adjunct to history and naked-eye examination, recognise safe pattern-based principles, and refer suspicious lesions without false reassurance.

Polarised and non-polarised devices reveal partly different structures. Contact fluid reduces reflection for non-polarised examination, while polarisation can display deeper vessels and shiny white lines. Know the instrument used because apparent absence of a feature may reflect technique.

A two-step approach first asks whether a lesion is melanocytic and then whether its architecture is benign or suspicious. Algorithms support, rather than replace, clinical judgement. Lesions outside competence, nodular change and discordance between history and image should be referred or sampled appropriately.

Dermatoscopy principles should answer a defined clinical question and be integrated with history, examination and the consequences of error. Explain uncertainty, record the sampling or observation conditions, and arrange a result-review plan rather than treating an isolated finding as self-interpreting.

Key points

  • Dermoscopy reduces surface reflection to reveal subsurface pigment and vascular structures that are not visible to the naked eye.
  • Start with lesion identity, history and naked-eye morphology; dermoscopy refines probability but does not independently diagnose every lesion.
  • Use a consistent algorithm within competence, looking for symmetry, colours, structures and melanoma-specific clues rather than one memorable sign.
  • Clean contact equipment, avoid cross-contamination, and use non-contact technique over broken skin unless the device can be safely protected and decontaminated.
  • For Dermatoscopy principles, describe what is seen before assigning a diagnosis, and record site, extent, symptoms, duration and change over time.
  • A technically adequate result in Dermatoscopy principles can still be misleading when the wrong lesion, site, preparation or clinical question was selected.

Indications, selection and cautions

Global architecture

Assess symmetry of colour and structure across axes before focusing on a single local clue; chaotic distribution increases concern.

Melanocytic structures

Pigment network, aggregated globules, streaks and homogeneous blue pigmentation can support melanocytic origin in the correct anatomical context.

Vascular morphology

Dotted, comma, hairpin, arborising or polymorphous vessels can refine differentials, but blanching pressure and contact fluid alter visibility.

Nodular warningRed flag

A firm growing or bleeding nodule may lack classic melanoma structures and requires urgent assessment based on history and examination.

Site-specific patterns

Face, palms, soles, nails and mucosa have specialised dermoscopic anatomy; general trunk rules cannot be transferred uncritically.

Red flags requiring action

  • A new or changing pigmented or non-pigmented lesion with asymmetry, ulceration, bleeding, nodularity or melanoma features needs the appropriate urgent cancer pathway regardless of a reassuring single image.

Method and interpretation

  1. 01
    Naked-eye lesion assessmentFirst step
    Why
    Establish the clinical context before magnification.
    Interpretation and limitations
    Record duration, evolution, symptoms, size and morphology; dermoscopy cannot correct an incorrect site or incomplete history.
  2. 02
    Polarised dermoscopy
    Why
    Visualise pigment, vascular architecture and deeper reflective structures.
    Interpretation and limitations
    Inspect systematically and save an image only with consent; pressure may blanch vessels and immersion may obscure scale.
  3. 03
    Baseline clinical photography
    Why
    Support short-interval monitoring when specialist judgement selects surveillance.
    Interpretation and limitations
    NICE recommends baseline photography for an atypical melanocytic lesion not excised at first presentation in secondary or tertiary care, with review after three months.
  4. 04
    Histopathological assessment
    Why
    Resolve lesions selected for biopsy or excision.
    Interpretation and limitations
    Sampling must match the clinical question and suspected malignancy; a partial biopsy can miss the most diagnostic or deepest focus.

Clinical next steps

01Planned assessmentUse dermatoscopic examination systematicallyFirst stepThe patient is stable and the result will alter diagnosis, referral or follow-up.+
  1. 1Define the question for Dermatoscopy principles, explain the process and obtain valid consent before exposing, touching, photographing or sampling skin.
  2. 2Choose representative anatomy, optimise lighting or specimen technique, and document site, morphology, symptoms and relevant previous treatment. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
  3. 3Interpret the result beside the full clinical pattern, communicate uncertainty and arrange ownership of results and safety-netting. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
02Uncertain resultResolve discordance in Dermatoscopy principlesThe technical finding conflicts with the history, lesion evolution or wider examination.+

Risks, monitoring and follow-up

  • Record who will review the result arising from Dermatoscopy principles, the expected timescale and the action threshold before the patient leaves.
  • Compare subsequent findings with the original site description, dimensions, symptoms and image or specimen identifiers for Dermatoscopy principles.
  • Reassess earlier if rapid growth, bleeding, ulceration, fever, mucosal disease, eye symptoms or functional compromise develops. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
  • Document technical limitations and previous treatment that could alter sensitivity or specificity of dermatoscopic examination.
  • Close the loop after specialist or laboratory review, including clinicopathological disagreement and any need for repeat sampling. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.

Special situations

Technique changes findings

Polarisation, contact pressure and fluid affect which white lines, vessels and superficial structures become visible.

Chaos precedes clues

An asymmetric lesion with disordered colour and structure deserves focused search for malignancy features and clinical correlation.

Pink lesions still matter

Amelanotic melanoma and other cancers may present mainly through vessels, ulceration and change rather than brown pigment.

Anatomy rewrites rules

Parallel-ridge concern on acral skin and facial pseudonetwork require site-specific competence before interpretation.

Monitoring is selective

Serial imaging is appropriate only when the surveillance decision itself is safe and a reliable recall system exists.

Common pitfalls

  1. 01

    Calling a lesion benign because one reassuring dermoscopic feature is present despite documented rapid growth.

  2. 02

    Pressing firmly enough to erase diagnostically useful vessels in a pink or amelanotic lesion.

  3. 03

    Applying trunk-based pigment-network rules unchanged to face, nail, palm or sole anatomy.

  4. 04

    Photographing without recording exact site and scale, making later comparison unreliable.

  5. 05

    Using monitoring to postpone referral for a nodular, ulcerated or otherwise high-risk lesion.

Practice

Two practice questions

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Question 1 of 2
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DermatologyOriginal SBA

Atypical lesion monitoring

A secondary-care dermatologist decides not to excise an atypical melanocytic lesion at first presentation. What monitoring step aligns with NICE guidance?

Choose one answer, then submit
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Sources and review status3 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE NG14 melanoma assessment and managementDermoscopy, baseline photography and specialist assessment recommendations.
  • NICE NG12 suspected cancer recognition and referralUrgent referral features for suspected skin malignancy.
  • Primary Care Dermatology Society dermoscopy overviewPattern recognition, equipment and safe diagnostic boundaries.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
1
Recheck identity, site, timing, preparation, treatment exposure and whether the selected target was genuinely representative. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
  • 2Repeat or select a complementary test only when it can distinguish the remaining important alternatives. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
  • 3Seek dermatology, pathology, microbiology or allergy advice when clinicopathological disagreement would change urgent care. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
    • 03Urgent patternDo not let dermatoscopic examination delay escalationEscalationA rapidly progressive eruption, systemic illness, threatened vision or airway, or suspected aggressive malignancy is present. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.+
    1. 1Stabilise immediate physiological threats and obtain same-day senior or specialty assessment according to the dominant emergency. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
    2. 2DefinitiveTake time-critical images or specimens only when doing so will not postpone resuscitation, antimicrobials or definitive referral. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.
    3. 3Record evolution and communicate the differential, outstanding results and explicit deterioration triggers during handover. Apply that step specifically within the dermatoscopy principles assessment and its recorded clinical context.