Preoperative measurement of thickness of cutaneous melanoma using high-resolution 20 MHz ultrasound imaging: A monocenter prospective study and systematic review of the literature

Abstract

Histologic measurement of the thickness of melanoma is a major prognostic factor and governs the size of the surgical excision (1cm for melanomas less than 1 mm thick, 2 cm for melanomas thicker than 2 mm and 3 cm beyond 4 mm). To determine whether high-resolution ultrasound can be used to predict surgical margins and, thus, to operate on patients in a single procedure avoiding further re-excision, we performed a systematic review of studies published from January 1987 to June 2007 and a prospective study. The systematic review selected 14 studies comparing histologic and ultrasound measurements and showing correlation coefficients generally greater than 0.9. Data available from 7 of the 14 studies (total 869 patients) showed predictive values of adequate margins in at least 72% of lesions using preoperative measurement of ultrasound thickness. The prospective study included 31 patients referred with a primary melanoma from March 2005 to March 2007. Ultrasound measurement of thickness was possible except for thin melanomas (<0.4 mm) in areas with marked photoaging, in the plantar zone, and in the case of very thick melanomas exceeding the explored depth (7.6 mm). The average thickness was 1.96 mm measured by ultrasound (SD: 2.15) and 1.95 mm by histology (SD: 2.62) and the Bland and Altman graph showed moderate agreement between ultrasound and histology. Limits of agreement were estimated at -1.4 and +1.8, corresponding to relative limits of agreement of -40 to +80%. Ultrasound predicted appropriate margins (1, 2 or 3 cm wide according to sonometric thickness) in 26 of the 31 subjects (84%, 95% CI 66-95). Preoperative high-resolution ultrasound is a noninvasive examination that can help in choosing appropriate surgical margins and should reduce the need of partial or excisional biopsy before surgery, and the need for further re-excision.