Background Early diagnosis and rapid surgical excision are essential for improving the prognosis of patients with melanoma. Reflectance confocal microscopy has been validated as a feasible procedure for in vivo diagnosis of melanoma but cannot be used to measure tumour thickness. However, ultrasonography and optical coherence tomography may allow melanoma thickness to be measured in vivo. Objectives To validate the accuracy and reliability of high-frequency ultrasonography (HFUS) and optical coherence tomography for assessing melanoma thickness in vivo. Methods We conducted a prospective study on 131 patients with at least one equivocal melanocytic lesion. Each lesion underwent optical coherence tomography and HFUS assessment, followed by excision and pathological examination. Histopathology was considered to be the gold standard for assessing melanoma thickness. Repeatability, inter- and intrarater reproducibility and reliability were evaluated for each imaging procedure. Results Ultrasonography showed a good level of agreement with histology [intraclass correlation coefficient (ICC) 0·807; 95% confidence interval (CI) 0·703-0·877] and excellent inter-rater reproducibility (G = 0·97), resulting in reliable in vivo assessment of melanoma thickness. The 930-nm optical coherence tomography showed a poor level of agreement with histopathology (ICC 0·0; 95% CI -0·2-0·2) and the inter-rater reproducibility was null (G = 0·00). Conclusions HFUS is a reliable and reproducible noninvasive method for assessing melanoma thickness. Routine use of HFUS may allow single-step excision of equivocal melanocytic lesions, with surgical margins determined by in vivo assessment of tumour thickness. What's already known about this topic? Early diagnosis and complete surgical excision with defined margins, depending on tumour thickness, is the recommended strategy for improving melanoma prognosis. Most primary melanomas require a two-step surgical procedure, with excision of the tumour followed by re-excision determined by histopathological assessment of tumour thickness. What does this study add? High-frequency ultrasonography is a reliable tool that provides reproducible results for in vivo evaluation of melanoma tumour thickness. This method could enable single-step surgical excision of melanoma.
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