Melanoma histological Breslow thickness predicted by 75-MHz ultrasonography

Background Ultrasound at 20 MHz tends to overestimate melanoma Breslow thickness due to lymphocytic infiltration or naevus remnant. Objectives To determine the efficacy of 75-MHz ultrasound for estimating melanoma thickness and to assess its reliability to predict surgical requirement. Methods One hundred and twelve suspicious skin lesions were imaged prospectively with the 75-MHz ultrasound in A and B mode. This instrument has a penetration of 3 mm and a lateral resolution of 21 mu m. Measurements were performed by two observers and the mean was compared with the histological Breslow thickness. Results Forty-five of 52 melanomas and 22 of 36 naevi had clear hypoechogenicity boundaries. The median histological Breslow thickness of melanomas was 0.4 mm and 22 were in situ. The median percentage error of the machine was 13% of the histological Breslow thickness, with a high correlation (Pearson's r = 0.908, P < 0.001). Measurement was highly reliable for invasive melanoma, even in the presence of lymphocytic infiltration or naevus. Conclusions In this series, 75-MHz measurement was highly reliable for predicting invasive melanoma thickness.