study demonstrated the accuracy of SCC measurement with HFUS by comparing SCC depth to histometry, noting a correlation to the 100th of a millimeter [51]. Despite this correlation, ultrasonographic examination of SCCs can be limited by the presence of an acoustic shadow artifact due to the refection of ultrasound waves by thickened, hyperkeratotic stratum corneum, which may obscure lesion boundaries [48, 52]. Terefore, ultrasound has suggested use as a complementary tool to support the pre-operative evaluation of SCC but not as the sole method of diagnosis [50]. An additional form of non-melanoma skin cancer studied with HFUS is mycosis fungoides (MF) [53, 54]. MF is characterized by presence of a SLEB, which researchers have noticed can be helpful for identifying response to therapy and disease remission; in two separate studies of patients with MF, thinning or complete disappearance of the SLEB corresponded with disease severity and completion of therapy, supporting the utility of HFUS as an objective tool in routine clinical practice [53, 55]. Melanoma In the study of melanoma, ultrasound demonstrates a homogenous hypoechoic lesion. Te shape of the lesion often correlates to the histologic subtype of the melanoma. For example, nodular melanoma will typically present with a spherical hypoechoic lesion, while a superfcial spreading melanoma will present with a thinner, lenticular, hypoechoic lesion subjacent to the epidermal entry echo [13]. Although no distinct ultrasonographic features of melanoma have been described, one important strength of ultrasound is its ability to predict Breslow thickness of a melanoma [48, 56]. Tis correlation with histologic thickness, the current gold standard on which melanoma staging and surgical planning rests, is predicted to be over 92% [57]. When compared to other techniques like OCT, ultrasound has superior correlation with histology, repeatability and inter-rater reliability [58]. Where OCT tends to underestimate Breslow Fig. 4 Nodular basal cell carcinoma measuring 5 mm by 7 mm on the left lower cheek of a 66-year-old man. Note the pearly borders and central ulceration in the gross photograph (a), the polymorphous vessels and ulceration in the dermatoscopic photo (b), and the 5 mm hypoechoic lesion in the superfcial dermis across the short axis of this biopsy-supported nodular basal cell carcinoma using a 50-MHz UHFUS probe (Longport, Inc. EPISCAN) Levy et al. Ultrasound J (2021) 13:24 Page 6 of 12 thickness, ultrasound has been shown to modestly overestimate tumor thickness [58]. Te cause of this overestimation is thought to result from the technology’s inability to distinguish an infammatory infltrate from melanocytic proliferation and neovascularization. Another contributing factor may be the desiccation of tissue as it is processed for histologic review. Nevertheless, its ability to resolve well beyond the dermis renders HFUS superior to other imaging modalities in predicting Breslow thickness [59]. Tough melanomas have been distinguished from benign melanocytic proliferations with specifcities as low as 30%, the addition of color Doppler sharply improves ultrasound as a diagnostic tool [43]. Melanomas have been shown to demonstrate more dense vascularization than benign nevi and exhibit low-fow arterioles. In another study of pigmented lesions, the direction of intralesional blood fow demonstrated a 100% specifcity in distinguishing melanoma from nonmelanoma tumors [46, 60]. Single‑center experience with 50‑MHz ultrasound device In a single-center experience with a 50-MHz device, the Longport, Inc. EPISCAN, the authors examined ultrahigh-frequency ultrasound biomicrographs of nearly 70 cutaneous lesions as well as normal skin and adnexae. Transducer power gain and time-gain compensation (TGC) were set to the device’s default settings—100% and 10%, respectively, with a TGC start of 0%. Skin position, or distance between transducer and impermeable membrane barrier, or skin, was 7.5 mm. Scanning depth ranged from 3.8 mm to 15.0 mm, with a scan length of 15 mm at a rate of 1 scan per frame per second. A standard acquisition protocol was followed. Te protocol included a horizontal (cranial–caudal) scan