povidone-iodine and Keratoacanthoma

While dermatoscopy improves diagnostic accuracy for raised nonpigmented lesions, those with white surface keratin can be problematical. We investigated whether retention of povidone-iodine by surface keratin provides a clue to benignity.. We performed a retrospective pilot study (n = 57) followed by a prospective study (n = 117) on raised nonpigmented lesions with white surface keratin. An initial dermatoscopic image was taken of each lesion, povidone-iodine was applied and another image taken. Following lavage with 70% ethanol, a third image was acquired. The percentage surface area of residual povidone-iodine staining after lavage was recorded, and the results analysed.. The optimal cut-off point of residual staining was 80%, where values of ≤80% pointed to malignancy. At this cut-off, the OR for lesions with values ≤80% to be truly malignant in the retrospective set was 4.03 (95% CI: 2.1-7.6) and the AUC was 0.7 (95% CI: 0.62-0.78). For the prospective set, the corresponding OR was 2.3 (95% CI: 1.4-3.7) and the AUC was 0.62 (95% CI: 0.55-0.68).. This study presents evidence that povidone-iodine retention may have a degree of efficacy in distinguishing benign from malignant keratotic lesions. Further study is warranted.

Topics: Aged; Aged, 80 and over; Area Under Curve; Carcinoma, Squamous Cell; Coloring Agents; Dermoscopy; Diagnosis, Differential; Female; Humans; Keratoacanthoma; Male; Middle Aged; Pilot Projects; Povidone-Iodine; Prospective Studies; Retrospective Studies; ROC Curve; Skin Neoplasms