Seborrheic keratosis or verruca plana? A pilot study with confocal laser scanning microscopy

Differentiation of some seborrheic keratosis (SK) and verruca plana (VP) lesions is a challenge. Confocal laser scanning microscopy (CLSM) has been proved to be useful in the diagnosis of skin diseases; however, to date, there is no report on the differential study of the two diseases with CLSM.

To obtain the CLSM image characteristics of SK and VP, and then test the differential ability of CLSM imaging.

We recruited 10 patients with typical lesions of SK under CLSM images to validate the features reported. Another 10 patients with typical VP lesions were also recruited, imaged with CLSM and biopsied to obtain the features under CLSM images based on histology analysis. Then, we attempt to summarize and refine those characteristics collected to obtain the most significant ones. All the cases with lesions suggestive of SK or VP were advised to undergo imaging with CLSM, and if CLSM imaging reflected discordantly with the clinical diagnosis, a biopsy was suggested for the exact lesion imaged. Those cases with CLSM and histology results were collected. Finally, two clinical dermatologists, who had no previous experience with CLSM, were tested with the simplified features of CLSM images to differentiate the suspected lesions of SK and VP among the cases collected.

In total, there were 58 cases with CLSM images and histology results collected, in which, 40 cases were diagnosed as SK and 18 cases as VP by histology. The two blinded dermatologists' judgments were identical to histology analysis.

CLSM proved to be valuable in the differential diagnosis of SK and VP. The simplified characteristics were easily understood and acceptable to those with no previous experience of CLSM.