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White circles, blood spots differentiated SCC from other lesions in dermoscopy

White circles, keratin and blood spots provided guidance in differentiating squamous cell carcinoma and keratoacanthoma from other raised nonpigmented skin lesions by dermoscopy, according to study results.

Researchers in Brisbane, Australia, conducted a retrospective analysis of 60 invasive squamous cell carcinoma (SCC) and 43 keratoacanthoma cases from 80 patients (mean age, 68 years; 26.3% women). They also performed a prospective analysis of 186 patients (mean age, 65 years; 32.8% women) with 206 raised, nonpigmented lesions. Sensitivity, specificity, predictive values and odds ratio were used as outcome measures.

Keratin, surface scale, blood spots, white structureless zones, white circles and coiled vessels were found in the analysis of the SCC and keratoacanthoma cases. Researchers then evaluated the criteria significance in the lesions (32 SCCs, 29 keratoacanthomas and 145 other lesions). Similar to the retrospective study results (51.2% vs. 30%; P=.03), central keratin was observed more frequently in keratoacanthomas than in SCCs (72.4% vs. 40.6%; P=.01) under prospective review.

Keratoacanthoma and SCC were related to the highest sensitivity for keratin (79%) and highest specificity with white circles (87%). Positive predictive values of keratin and white circles were 92% and 89%, respectively, when basal cell carcinoma was contrasted with keratoacanthoma and SCC. When contrasted with actinic keratosis and Bowen disease, SCC and keratoacanthoma had a positive predictive value of 50% for keratin and 92% for white circles. White circles (OR=6.1, 2.4-13.3), keratin (OR=3.6, 1.5-8.7) and blood spots (OR=2.6, 1.1-6.3) acted as independent predictors of SCC and keratoacanthoma in multivariate analysis (95% CI for all).Interobserver agreement for white circles being present or absent on dermoscopy was rated as good (0.55; 95% CI, 0.44-0.65).

“We have provided new evidence that dermoscopy is helpful for nonpigmented lesions beyond the diagnosis of amelanotic melanoma,” the researchers concluded. “The diagnostic utility of white circles is a new dermoscopic finding. It is relevant and reliable and shows high specificity and a high positive predictive value in differentiating keratoacanthoma and SCC from other raised, nonpigmented lesions.”