Test Characteristics of High-Resolution Ultrasound in the Preoperative Assessment of Margins of Basal Cell and Squamous Cell Carcinoma in Patients Undergoing Mohs Micrographic Surgery

Abstract

Background Non-invasive techniques to assess subclinical spread of non-melanoma skin cancer (NMSC) may improve surgical precision. High frequency ultrasound (HIFU) has shown promise to evaluate the extent of NMSC. Objective To determine the accuracy of HIFU to assess the margins of basal cell (BCC) and squamous cell carcinomas (SCC) prior to Mohs micrographic surgery (MMS). Methods We enrolled 100 patients with invasive SCC or BCC. Prior to the first stage of MMS, a Mohs surgeon delineated the intended surgical margin. Subsequently, a trained ultrasound technologist independently evaluated disease extent using the EPISCAN I-200 to evaluate tumor extent beyond this margin. The accuracy of HIFU was subsequently tested by comparison to pathology from frozen sections. Results The test characteristics of the ultrasound were sensitivity= 32%, specificity= 88%, positive predictive value= 47%, and negative predictive value=79%. Subgroup analyses demonstrated improved test characteristics for tumors larger than the median (area >1.74 cm2). Qualitative analyses showed that HIFU was less likely to identify extension from tumors with subtle areas of extension, such as small foci of dermal invasion from infiltrative SCC and micronodular BCC. Conclusions HIFU requires additional refinements to improve the preoperative determination of tumor extent prior to surgical treatment of NMSC.

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