Melanoma: Diagnosis

ACRAL PIGMENTED LESIONS

• A diagnostic flow chart for acral pigmented lesions can be found here.  The paper that contains that algorithm is a good summary of diagnosis and management of acral pigmented lesions. 37556446

• The BRAAFF checklist is another approach to the diagnosis of acral melanoma. 26211689

• Nail bed pigmented lesions in children are VERY uncommonly malignant.  Congenital nevi result in breaking of a lot of the typical diagnostic guidelines. (Dermoscopy Excellence) 

FACIAL PIGMENTED LESIONS

• The differential of facial pigmented lesions on the face primarily includes solar lentigo and seborrheic keratosis. 

• The reticular network on the face is NOT suggestive of a melanocytic lesion.  This is in strict contrast to the trunk and extremities.  A reticular pattern on the face is usually indicative of a solar lentigo or reticulated seborrheic keratosis.  

• One useful diagnostic algorithm is the inverse approach which excludes melanoma by focusing on 6 non-melanoma features to make the diagnosis of an solar lentigo or seborrheic keratosis in lieu of a melanoma. 32592885​​

Inverse Approach - 6 non-melanoma features (28761960)

• Examples of these criteria can be found here.

Actinic Keratosis

1. Scales (pigmented or non-pigmented)

2. White and wide follicles or rosettes

3. Erythema or reticular vessels

Solar Lentigo/Seborrheic Keratosis

1. Lines - reticular or parallel (fingerprint-like patterns)

2. Sharp demarcation

3. Classic SK criteria

PATHOLOGY 

• Providing clinical information to the pathologist may improve inter-rater reliability and prevent missing evolving melanomas.  It results in upgrading, and the impact of this as a positive or negative is unclear. 39476175

GENETIC TESTS

Tape Stripping

• DermTech is a genetic test that measures genomic atypic by measuring RNA LINC00518 and PRAME, and anti-DNA TERT.  The sample is obtained by stripping superficial layers of skin with tape.   

• In a review of 44 cases for which a biopsy was performed after a DermTech test was performed (because of a positive test result, or clinical concern), it correctly identified 9 of 10 melanomas (5 in situ, 4 invasive) and missed 1 LM.  Of 14 non-nevi, it incorrectly gave positive results to 11.  2 out of 2 severely dysplastic nevi were given positive results.  15 out 17 mild, moderate, or nevi otherwise considered to be of low malignant potential were classified as positive.  Because many negative test results did not receive biopsy, sensitivity and specificity cannot be calculated, but this does highlight the relatively inaccurate nature of the test, particularly with respect to false positive results (~68% of results in this cohort were false positives).  37549792

TOTAL BODY PHOTOGRAPHY​

3D Total-Body Photography in Patients at High Risk for Melanoma: A Randomized Clinical Trial. JAMA Dermatol. 2025 May. PMID: 40136310.

• Population: 314 adult participants (≥18 years) at high risk for melanoma were enrolled in Brisbane, Australia. High-risk criteria included: prior melanoma diagnosis (before age 40 or multiple before age 65), strong family history of melanoma (2 or more 1st degree relatives), genetic risk (known pathogenic gene mutation), or dysplastic nevus syndrome (multiple clinically atypical nevi + family history).

• Intervention: Participants in the intervention group received usual care plus in-person 3D TBP and SDDI (sequential digital dermoscopy imaging) every 6 months with remote teledermatology review by a senior dermatologist; PLUS they had in person evals by junior clinicians at the time of imaging.  Control group received usual care and follow-up surveys only.  Usual care was up to discretion of GP or dermatologist, and was assessed at baseline but not confirmed.  Most patients were seen yearly or more frequently, with a plurality being seen every 6 months.  There was no statistical difference between these frequencies amongst intervention and control but it did approach statistical significance (p=0.06).  These "usual care" providers WERE AWARE of their patients status as an intervention or control patient. 

• Outcome Measures: Number and rate of excisions/biopsies, histopathologic findings (melanoma, keratinocyte cancer, benign lesions) over 2 years of enrollment per patient.

• Results:

  • Excisions: More in the intervention group (mean 5.73 vs. 3.99 per person, P = .02).

  • Melanomas: Fewer diagnosed in the intervention group (24 vs. 43), incidence rate significantly lower (2.03 vs. 3.62 per 10,000 person-days, P = .02).

  • Keratinocyte cancers: Higher in intervention group (1.62 vs. 0.94 per person, P = .03).

  • Benign lesions: More benign lesions excised in the intervention group.

  • No significant difference in per-person melanoma diagnosis rates or invasive melanoma rates (the difference in average melanomas per participant was not statistically significant due to averaging across all participants and clustering of multiple melanomas in a few individuals). It approached SS, p=0.06)

• Editorial insight: ​Despite technological promise, the intervention did not improve melanoma detection. In fact, the intervention group had fewer melanomas diagnosed than the control group, which is a failure by basic screening standards. 40136264 A companion cost-effectiveness analysis found higher costs in the intervention group, no clinical benefit, and a 95.4% probability that TBP/SDDI was both more expensive and less effective than usual care. 40136266

• My personal view was that there wer enough methodological flaws that this does prove that TBP cannot be used to surveil skin.