Usefulness of high‐frequency ultrasound in differentiating basal cell carcinoma from common benign pigmented skin tumors

Abstract Background Basal cell carcinoma (BCC) is the most common cutaneous malignancy. Occasionally, it may have an appearance similar to that of some benign pigmented skin lesions. Therefore, additional information is needed to differentiate these lesions. Materials and Methods A diagnostic accuracy study was performed from February 2018 to April 2019. All lesions underwent ultrasound examination with 50 and 20 MHz probes. The high‐frequency ultrasound (HFUS) images were evaluated independently by 2 experienced doctors for the presence of predefined features, including the depth, shape, margin, anechoic area, hyperechoic spots, epidermal interrupted echo, mushroom sign, flat‐bottom sign, and superficial hyperechoic focus (SHEF). Results A total of 54 BCCs, 51 melanocytic nevi and 55 seborrheic keratoses (SK), were included. BCCs often involved the subcutaneous tissue (11/54, 20.4%; P < .001) and had an irregular shape (26/54, 48.1%; P < .001) and ill‐defined borders (26/54, 48.1%; P < .001), while most benign pigmented lesions had a regular shape (101/106, 95.3%; P < .001) and well‐defined borders (95/106, 89.6%; P < .001). BCCs occasionally showed anechoic areas (10/54, 18.5%; P < .001) and epidermal interrupted echo (18/54, 33.3%; P < .001). Moreover, hyperechoic spots could be found in BCCs (43/54, 79.6%), nevi (27/51, 52.9%), and SK (30, 54.5%) ( P = .001), with mean number of 7.3, 5.5, and 8.0, respectively. The mushroom signs were all present in melanocytic nevi (18/51, 35.3%), while the flat‐bottom sign (43/55, 78.2%; P < .001) and SHEF (40/55, 72.7%; P < .001) presented mainly in SKs. Conclusions Based on the typical features, HFUS could improve the accuracy of BCC identification and should be considered when dermatologists are unsure about the lesion type.