High-frequency ultrasound accuracy in preoperative cutaneous melanoma assessment: A meta-analysis

Abstract

Background: High-frequency ultrasound (HFUS) can safely and efficiently visualize cutaneous tumour characteristics including depth.

Objectives: We aimed to evaluate its accuracy in measuring melanoma depth against the gold standard, histopathology, for treatment planning.

Methods: A review of publications was conducted in March 2023 through five electronic databases. Thirty-six included articles studied patients who received HFUS (≥10 MHz) measurements, melanoma biopsy or excision, and reported a tumour depth correlation coefficient between HFUS and histopathology. We analysed correlation coefficients between HFUS and histopathology, measured tumour depths and shed light on reasons for mismeasurements. Additionally, we identified the reporting of critical metrics including, lesion characteristics, melanoma subtype, type of correlation coefficient, 95% confidence intervals for Pearson coefficients and sample size.

Results: The most common tumour imaged was superficial spreading melanoma on the trunk and extremities, followed by head/face. Maximum ultrasound frequencies ranged from 13 MHz to 100 MHz with participants ranging from 5 to 264. Histopathology and HFUS correlation coefficients ranged from 0.417 to 0.997 (median: 0.94, mean: 0.89 and SD: 0.13). Lower frequency probes (10-20 MHz) were less accurate in assessing melanoma thickness, with a cumulative mean correlation coefficient of 0.87 compared to 0.94 (20-25 MHz) and 0.98 (≥70 MHz). Studies demonstrated higher sonographic accuracy in melanomas >0.75 mm. Additionally, ultrasound may report increased melanoma depth compared to histopathology for reasons including lymphocytic infiltration, presence of a nevus and shrinkage during specimen processing. Furthermore, we found a gap in the reporting of details such as fundamental characteristics of lesion populations. Specifically, 86% (31 out of 36) of the studies failed to report one or more critical metrics, such as mean, median or range of lesion depths.

Conclusions: HFUS may serve as a supplementary tool for preoperative melanoma assessment, with increased accuracy in thicker tumours. Frequencies <20 MHz are less reliable in assessing depth. Frequencies ≥70 MHz demonstrate stronger correlations to histopathology. Higher ultrasound accuracy was seen for melanomas with Breslow depth >0.75 mm.

FIGURE 1

PRISMA flowchart.

FIGURE 2

Individual study effect sizes and 95% confidence intervals. Hinz et al. is not plotted due to confidence interval width larger than 1.0. Rompel et al. is not plotted due to inability to calculate 95% CI secondary to lack of population (n) value. Kaikaris et al. is not plotted due to lack of total correlation coefficient provided.

FIGURE 3

Comparison of correlation coefficients across studies stratified by sonographic frequency. Error bars were calculated by standard error of the mean. <20 MHz, , , , , ; 20–25 MHz, , , , , , , , , , , , , , , , , , , , , , : 30–50 MHz, , : ≥70 MHz., , ,

FIGURE 4

Summary of factors for high correlation between high‐frequency ultrasound (HFUS) and histopathology. Frequencies 70 MHz or greater have even stronger correlations than 20 MHz.