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 Noninvasive techniques to assess subclinical spread of nonmelanoma skin cancer (NMSC) may improve surgical precision. High-resolution ultrasound has shown promise in evaluating the extent of NMSC. OBJECTIVES To determine the accuracy of high-resolution ultrasound to assess the margins of basal cell (BCC) and squamous cell carcinomas (SCC) before Mohs micrographic surgery (MMS). METHODS We enrolled 100 patients with invasive SCC or BCC. Before 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 high-resolution ultrasound was subsequently tested by comparison with pathology from frozen sections. RESULTS The test characteristics of the high-resolution ultrasound were sensitivity=32%, specificity=88%, positive predictive value=47%, and negative predictive value=79%. Subgroup analyses demonstrated better test characteristics for tumors larger than the median (area>1.74 cm2). Qualitative analyses showed that high-resolution ultrasound 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. CONCLUSION High-resolution ultrasound requires additional refinements to improve the preoperative determination of tumor extent before surgical treatment of NMSC.