19.3 Non-Invasive Skin Imaging, Skin Function Measurement, Teledermatology & Skin Cancer Surveillance
Key Takeaways
- Short-term sequential digital dermoscopy, repeated after about 3 months, is used for flat equivocal melanocytic lesions without melanoma-specific features, and any significant change leads to excision.
- Reflectance confocal microscopy uses near-infrared light (about 830 nm) to produce horizontal images with near-cellular resolution to a depth of about 200 to 250 micrometres.
- Organ transplant recipients have a roughly 65- to 100-fold increased risk of cutaneous squamous cell carcinoma, and switching to an mTOR inhibitor or starting low-dose acitretin can reduce new tumours in high-risk patients.
- In the ONTRAC trial, oral nicotinamide 500 mg twice daily reduced new keratinocyte cancers by about 23% in immunocompetent high-risk patients, but a later trial in transplant recipients showed no significant benefit.
- Since 2008, people aged 35 and older with German statutory health insurance have been entitled to a skin cancer screening examination every 2 years.
Last updated: September 2026
19.3 Non-Invasive Skin Imaging, Skin Function Measurement, Teledermatology & Skin Cancer Surveillance
Dermoscopy itself is covered in the dermoscopy chapter. This section covers the other imaging tools and how they are used for surveillance.
Sequential Digital Dermoscopy and Total Body Photography
| Tool | How It Is Used | When to Excise |
|---|---|---|
| Short-term sequential digital dermoscopy | Repeat dermoscopic images after about 3 months for single flat, equivocal melanocytic lesions without melanoma-specific features | Any significant change in structure, colour, or asymmetric growth |
| Long-term digital follow-up | Images every 6–12 months for many naevi in high-risk patients | New structures, asymmetric enlargement, regression, new colours |
| Total body photography (2D or 3D) | Whole-body images to detect new or changing lesions; combined with digital dermoscopy ("two-step" surveillance) | New lesions in adults, or change in existing ones |
Nodular, raised, or rapidly growing lesions must not be monitored. They need excision, because nodular melanoma can grow fast.
Reflectance Confocal Microscopy (RCM)
- Uses near-infrared laser light (about 830 nm) to produce horizontal (en face) grey-scale images with near-cellular resolution, down to about 200–250 µm (the papillary dermis).
- Melanocytic lesions: melanoma shows pagetoid cells and atypical cells at the dermo-epidermal junction, with loss of the normal honeycomb pattern. RCM added to dermoscopy reduces benign excisions.
- Lentigo maligna: helps diagnosis and mapping margins on the face.
- Basal cell carcinoma: tumour islands with polarised nuclei and peripheral palisading.
- Ex vivo confocal microscopy can assess margins during micrographic surgery.
Optical Coherence Tomography (OCT)
- Produces vertical (cross-sectional) images to a depth of about 1–2 mm with lower resolution than RCM.
- Best for keratinocyte tumours: diagnosing and subtyping BCC, monitoring non-surgical treatment, and assessing actinic keratoses. Dynamic OCT shows vessels.
- Line-field confocal OCT combines vertical and horizontal imaging at cellular resolution.
High-Frequency Ultrasound (HFUS)
- Probes of about 20–100 MHz image the skin and subcutis.
- Uses: preoperative tumour depth (BCC, melanoma), inflammatory disease (morphoea activity, hidradenitis suppurativa, where ultrasound finds subclinical tunnels and collections and refines staging), nails, and cysts.
- Lymph node ultrasound is more sensitive than palpation for detecting nodal recurrence and is part of melanoma follow-up for higher-risk stages in European guidance.
Measuring Skin Function
| Measurement | What It Shows |
|---|---|
| Transepidermal water loss (TEWL) | Barrier function; raised in atopic dermatitis and irritant dermatitis |
| Corneometry | Stratum corneum hydration |
| Sebumetry | Sebum output |
| Colorimetry and spectrophotometry | Erythema and pigmentation, for example in phototesting |
| Skin surface pH | Barrier and microbiome environment |
| Elasticity (cutometer) | Mechanical properties, for example in scleroderma or ageing |
These measurements are mainly used in research, clinical trials, and occupational dermatology.
Teledermatology and Artificial Intelligence
- Store-and-forward teledermatology sends clinical and dermoscopic images for specialist review. It is widely used for triaging suspected skin cancer. Live (real-time) consultations suit follow-up and inflammatory disease.
- Artificial intelligence (AI) classifiers can match specialists on selected image datasets. In the EU, diagnostic AI software is regulated as a medical device (Medical Device Regulation), and the EU AI Act classes medical AI as high-risk.
- Limitations: performance falls with images unlike the training data (dataset shift), with underrepresented skin types, and with rare diagnoses. Clinicians remain responsible and must keep human oversight.
Skin Cancer Screening
- Germany runs a national programme: since 2008, people with statutory health insurance aged 35 and older can have a skin cancer screening examination every 2 years. The regional SCREEN pilot in Schleswig-Holstein was followed by lower melanoma mortality, but this was not reproduced nationally, and no randomised trial has proven a mortality benefit for population screening.
- Concerns: overdiagnosis of thin melanomas and cost.
- Targeted surveillance is widely recommended for high-risk people: over about 100 naevi or several atypical naevi, previous melanoma, two or more affected first-degree relatives or a known CDKN2A mutation, organ transplant recipients, genodermatoses such as xeroderma pigmentosum, and fair-skinned people with heavy sun damage.
- Euromelanoma is a pan-European awareness and screening campaign run by dermatologists.
Surveillance of Organ Transplant Recipients (OTRs)
- Solid organ transplant recipients have a roughly 65- to 100-fold increased risk of cutaneous squamous cell carcinoma, which is often multiple, aggressive, and more likely to metastasise. The usual BCC:SCC ratio is reversed.
- Skin examinations: before transplantation, then at least yearly; every 3–6 months once skin cancer has developed.
- Prevention: strict photoprotection; field treatment of actinic keratoses (5-fluorouracil, photodynamic therapy); and early treatment of all lesions.
- Chemoprevention: low-dose acitretin for patients with multiple SCCs. The benefit is lost when it is stopped.
- Immunosuppression: in agreement with the transplant team, switching from calcineurin inhibitors to an mTOR inhibitor (sirolimus or everolimus) reduces new SCCs in patients who have already had skin cancer. Azathioprine increases UVA photosensitivity. Long-term voriconazole (phototoxic) is associated with SCC and should be avoided where possible.
- Nicotinamide: in the ONTRAC trial, 500 mg twice daily reduced new keratinocyte cancers by about 23% in immunocompetent high-risk patients. A later trial in transplant recipients did not show a significant benefit.
Test Your Knowledge
A 42-year-old woman with many naevi has a flat, 6 mm pigmented lesion on her back that looks slightly different from her other naevi but shows no melanoma-specific dermoscopic features. What is an accepted management option?
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Test Your Knowledge
Which statement best describes reflectance confocal microscopy (RCM)?
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Test Your Knowledge
A 58-year-old kidney transplant recipient on tacrolimus and mycophenolate has had eight cutaneous squamous cell carcinomas in 2 years. Which measure is most likely to reduce new tumours, in agreement with the transplant team?
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Test Your Knowledge
What did the ONTRAC trial of oral nicotinamide show?
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