Three point checklist
In 2003, during the Virtual Consensus Net Meeting on Dermoscopy (CNMD) a simple algorithm, called three-point checklist, was established to distinguish malignant [i.e. melanoma and pigmented basal cell carcinoma (BCC)] from benign pigmented skin lesions.
The algorithm relies on the following criteria
- Asymmetry in structure and/or in color in one or two axis of the lesion. The contour shape of the lesion does not impact on the symmetry.
- Atypical network, defined as pigmented network with thickened lines and irregular distribution.
- Blue-white structures, namely any white and/or blue color visible in the lesion, including blue-white veil, scar-like depigmentation, and regression structures such as peppering.
The presence of more than one of these criteria is suggestive for melanoma (Fig. 1, 2, 3, 4)
In 2004 Soyer et al. demonstrated that the three-point checklist had a diagnostic value in screening procedure also when used by non expert. In their study, six non-experienced dermoscopists after a 1-hour introduction to the three-point checklist were asked to evaluate 231 clinically suspicious lesions using this algorithm. Finally, the non-experts were able to identify malignant pigmented skin lesions with a sensitivity of 96% and a specificity of 33%.
The pilot study was followed in 2006 by a larger one performed by Zalaudek et al. in order to revalue the preliminary results. The study was open both to experts and non-experts in dermoscopy who, after a short web-based dermoscopy training, evaluated dermoscopy images of 165 skin lesions following the aforementioned algorithm. The results showed good inter-observer reproducibility with a kappa value of 0.53, sensitivity of 91% (not influenced by the observers’ experience) and an overall specificity of 72% for malignancy (significantly influenced by observers’ skills). The best predictor of malignancy was asymmetry followed by the blue-white structures and atypical network.
In order to improve skin cancer screening and educational campaigns, one of us in 2006 tested in a prospective study if the adjunct of dermoscopy to the standard clinical examination of primary care physicians (PCPs) could improve the accuracy of skin cancer triage. After 1-day training course on dermoscopy, PCPs in Naples and in Barcelona were randomly assigned to the dermoscopy evaluation arm or naked-eye evaluation arm. During a 16-month period, 73 PCPs evaluated 2522 skin lesions in their clinics and scored them following the three-point checklist criteria. All patients were revalued by expert dermoscopists.
Sensitivity, specificity, positivity and negative predictive values were calculated for both arms. Significant differences were found in term of sensitivity and negative predictive value (p=0.002 in the naked-eye evaluation arm; p=0,004 in the dermoscopy evaluation arm). In conclusion dermoscopic criteria had shown to improve the ability of PCPs in skin cancer triage and to reduce useless expert consultation. However, further studies are necessary to define new dermoscopic algorithm allowing to easily distinguish also non-pigmented skin lesions such as amelanotic melanoma and non-pigmented BCC.
- Argenziano & Soyer: Dermoscopy of pigmented skin lesions--a valuable tool for early diagnosis of melanoma. Lancet Oncol. 2001;2:443-9. PMID: 11905739.
- Argenziano et al.: Dermoscopy of pigmented skin lesions: results of a consensus meeting via the Internet. J. Am. Acad. Dermatol. 2003;48:679-93. PMID: 12734496. DOI.
- Soyer et al.: Three-point checklist of dermoscopy. A new screening method for early detection of melanoma. Dermatology (Basel) 2004;208:27-31. PMID: 14730233. DOI.
- Zalaudek et al.: Three-point checklist of dermoscopy: an open internet study. Br. J. Dermatol. 2006;154:431-7. PMID: 16445771. DOI.
- Argenziano et al.: Dermoscopy improves accuracy of primary care physicians to triage lesions suggestive of skin cancer. J. Clin. Oncol. 2006;24:1877-82. PMID: 16622262. DOI.