The analysis and validation of the prediction value of conventional and contrast-enhanced ultrasonography for BRAF mutant papillary thyroid microcarcinoma

Background: BRAF has certain potential in distinguishing aggressive papillary thyroid microcarcinoma (PTMC). However, it is not recommended to conduct BRAF analysis for all suspicious thyroid nodules <1 cm. In order to investigate the ultrasound value indicating BRAF mutation among PTMC, which showed discrepancy in previous studies, we aimed to establish a predictive model based on conventional and contrast -enhanced ultrasonography.Methods: We consecutively and retrospectively enrolled patients with PTMC who underwent fine-needle aspiration biopsy (FNAB) at our hospital between January 2020 and January 2021. All PTMC patients received conventional and contrast-enhanced ultrasound prior to FNAB, samples gained went through cytological analysis and BRAF testing subsequently. The following conventional ultrasonography data were analyzed: maximum diameter, echogenicity, echo homogeneity, echogenic foci, location, shape, boundary, aspect ratio, and blood flow volume. Moreover, the following contrast-enhanced ultrasonography data were also analyzed: degree, homogeneity, completeness, and enhancement method. Time-intensity curves from contrast-enhanced ultrasonography were analyzed using VueBox software for different regions of interest, including the entire tumor, the area of strongest enhancement, and healthy thyroid glands. The independent risk factors for BRAF mutation in PTMC were identified using univariate and multivariate logistic regression. Their predictive value was tested through internal validation.Results: Of the 103 PTMC lesions analyzed, 72 involved BRAF mutations. Five independent ultrasonographic risk factors for BRAF mutation were identified: relative time to peak value in the area of strongest enhancement, unclear boundary, location adjacent to thyroid capsules, maximum diameter >0.5 cm, and punctate echogenic foci. A predictive model based on these factors was able to diagnose BRAF mutations in PTMC, with an area under the curve (AUC) of 0.824. During internal validation, this model showed an AUC of 0.723.Conclusions: Conventional and contrast-enhanced ultrasound characteristics, including relative time to peak value in the area of strongest enhancement, unclear boundary, location adjacent to thyroid capsules, maximum diameter >0.5 cm, and punctate echogenic foci, may be useful for predicting BRAF mutations in patients with PTMC.