Pearls of keratinizing tumors.

A LTHOUGH THE CLINICAL CHARACTERIStics of keratoacanthomas (KAs) are well known, there is limited information about their dermoscopic appearance and features. We evaluated 15 KAs and welldifferentiated squamous cell carcinomas (SCCs). Dermoscopic evaluation revealed that all lesions demonstrated a white to yellowish round structure surrounded by a white halo. Given the resemblance to a pearl, we named this structure a keratinizing pearl. The most likely histopathologic correlate of a keratinizing pearl seen under dermoscopy is a horn pearl within the epidermis. In fact, biopsy specimens were obtained from all lesions, and the findings of histopathologic analyses were consistent. Horn pearls have been described in the pathology literature as characteristic structures that are composed of concentric squamous cell layers with increasing keratinization toward the center. A dermoscopic image of a welldifferentiated SCC with keratinizing pearls is shown in Figure, A. Histopathologic analysis revealed keratinizing pearls within the epidermis (Figure, B). Dermoscopic images of a KA-type SCC with keratinizing pearls (Figure, C) and a KA (Figure, D) are also shown. In conclusion, “keratinizing pearls” seen on dermoscopy may be suggestive of a well-differentiated keratinizing tumor, such as a KA and/or a well-differentiated SCC.