Key points in dermoscopic diagnosis of basal cell carcinoma and seborrheic keratosis in Japanese.

Basal cell carcinoma (BCC) and seborrheic keratosis (SK) are representative pigmented skin tumors, and they are differentiated as non-melanocytic lesions in the two-step dermoscopy algorithm proposed by the Consensus Net Meeting on Dermoscopy. Because most BCC in Japanese patients are pigmented clinically, dermoscopy plays an important role in their differential diagnosis. The dermoscopic criteria for BCC include the lack of a pigment network and the presence of at least one positive feature for BCC, such as large blue-gray ovoid nests, multiple blue-gray globules, leaf-like areas, spoke wheel areas, arborizing vessels and ulceration. Whereas various dermoscopic features are seen in SK, comedo-like openings, milia-like cysts, and fissures and ridges are especially important features. It is necessary for clinicians to consider the pathological conditions causing the dermoscopic features of BCC and SK. In addition, the sensitivity and specificity of each feature should be taken into consideration to ensure an accurate dermoscopic diagnosis.