The seven-point checklist & melanoma incognito
The seven-point checklist
In the latter years, a lot of analytical methods based on scored algorithms have been introduced both to simplify the dermoscopic learning and to improve the early melanoma detection. The seven-point checklist, published in 1998, represents one of the most and latest validated dermoscopic algorithms due to its high sensitivity and specificity, also when used by non-experts. The seven criteria were originally tested on 342 melanocytic lesions (117 melanomas and 225 atypical nevi) and were chosen for their frequent association with melanoma. Three of them were defined as major criteria (atypical network, blue-white veil and atypical vascular pattern), whereas the remaining 4 were considered as minor (irregular streaks, irregular dots/globules, irregular blotches and regression structures)(Table 1).
To validate this algorithm, a univariate statistical analysis was used to determine differences between melanoma and nevi. A score of 2 points was assigned to the criteria with odds ratios > 5, (major criteria), while a score of 1 point was assigned to the criteria with odds ratios < 5 (minor criteria). A minimum total score of 3 allows identifying melanoma with a sensitivity of 95% and a specificity of 75%. In other words, at least two dermoscopic criteria (one major and one minor) must be present for a suspicious diagnosis. According to a revised, simplified seven-point checklist, the presence of at least one of the seven criteria should allow the diagnosis of melanoma with a sensitivity of 85-93% and a specificity between 45 and 48%.
In 2003 the various dermoscopic algorithms (classical pattern analysis, the ABCD rule, Menzies' method and the seven-point checklist) were re-evaluated and tested by non-experts. In details, 16 physicians not familiar with dermoscopy examined images of 20 pigmented lesions using the different methods, before and after an Internet-based training course on dermoscopy. The results showed a significant improvement in the dermoscopic diagnosis of melanoma after the Web training for pattern analysis with the ABCD rule and Menzies' method, but not for the seven-point checklist, which allowed higher sensitivity even before the web course. For this reason, the seven-point checklist is considered among the algorithms with the best sensitivity for the non-expert investigators. Afterwards, in the Consensus Net Meeting on Dermoscopy, the value of the seven-point checklist was definitively confirmed.
As previously mentioned, the seven-point checklist allows defining a lesion as suspicious when at least one minor and one major criteria are present (score of 3 or more). Although generally multiple malignant features are at same time present in a given melanoma, sometimes just one of them is prevalent. Particularly, this is true for lesions showing regression in more than 50 % of the lesion surface (Fig.5) or lesions with spitzoid features .
Melanoma incognito is defined as a difficult-to-diagnose melanoma, namely a lesion that appears clinically and, sometimes also dermoscopically, benign or borderline. However, the following 7 management rules can help dermatologists to detect melanomas mimicking benign lesions :
1: Do not use dermoscopy only for suspicious lesions
Melanomas may mimic clinically a variety of benign lesions as nevi, seborrheic keratosis, pyogenic granuloma and dermatofibroma. Dermoscopic examination on all skin lesions is the only way to identify lesions that appear clinically benign but are indeed malignant.
2: Excise lesions with unspecific pigmented pattern
Melanoma, especially the hypo/amelanoyic type, could not show dermoscopic features of melanocytic lesions and be confused with benign and inflammatory lesions. To avoid this mistake, if the pattern of a lesion is not suggestive to determine its nature, the biopsy is mandatory.
3: Biopsy spitzoid lesions
Starbust pattern, tipically associated with Spitz nevus of childhood, could be a melanoma clue in adulthood. Thus, all lesions with spitzoid features must be excised in adult patients.
4: Biopsy lesions revealing extensive regression features
Regression structures, namely white scar-like areas (corresponding to fibrosis) and blue pepper-like granules (corresponding to melanophages) are alarming bells also in the absence of other melanoma signs, especially in fair skin individuals with multiple nevi. A paper published in 2004 has demonstrated that the risk for a lesion to be a melanoma is directly correlated with the extent of regression seen with dermoscopy. Therefore, lesions showing significant regression structures (in particular more of 50 % of the lesion area) should always be excised independently from its additional dermoscopic features.
5: Biopsy lesions showing changes on short-term follow-up
About 10% of melanomas do not show at the baseline examination clear-cut clinical and dermoscopic features of malignancy. Therefore, flat lesions, moderately atypical, in patients with multiple atypical nevi, must be monitored with digital images and re-evaluated after a short-term follow-up (3 to 6 months). A rapid change at dermoscopic evaluation is sufficient to require excision. However, follow-up is not a good strategy for nodular lesions that must be immediately excised because also a short delay in the treatment of nodular melanoma might negatively impact on its prognosis.
6: Excise pink lesions with an atypical vascular pattern
Atypical vascular pattern, such as dotted and linear-irregular vessels, is a malignancy feature, especially for hypo-amelanotic lesions. Therefore, pink lesions showing these features, in absence of other melanoma criteria, should always be biopsied (Fig. 6).
7: Biopsy lesions without clinical-dermoscopic correlation
The lack of correlation between clinical and dermoscopic features is a sufficient reason to perform a biopsy. For example, a lesion that clinically appears like a dermal nevus but dermoscopically doesn't reveal the usual dermal nevus features, must be excised (Fig. 7).
Figure 7: This pigmented lesion, clinically resembling a dermal nevus, shows at dermoscopic examination blue-white veil in center, brown-black globules and whitish irregular lines. The lack of correlation between the clinical and dermoscopic features imposes the excision. Histopathologic diagnosis: melanoma (Breslow thickness: 0.9 mm)
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