Sonographic characteristics of thyroid nodules with a Halo.

Objective: To investigate the sonographic characteristics of thyroid nodules with a halo, explore the value of contrast-enhanced ultrasound (CEUS) combined with fine needle aspiration (FNA) in identifying nodules with a halo, and predict the risk of metastasis by analyzing the pathological features of the halo.

Methods: A retrospective analysis was conducted on 185 postoperative cases of thyroid nodules accompanied by halos between January 2019 and December 2022. After describing the ultrasound characteristics of the thyroid nodules and their halos, all patients were divided into three groups, the first group (group I = CEUS only) of patients underwent CEUS, the second group (group II = CEUS + FNA) underwent FNA based on the first group, and the third group (group III = FNA only) underwent FNA directly. The CEUS and FNA results were graded using the Chinese Thyroid Imaging Report and Data System (C-TIRADS) and Bethesda Reporting System for Thyroid Cytopathology, respectively. Those graded below C-TIRADS 4b or Bethesda IV were defined as benign, and the results of FNA were referenced when the two methods were combined. The surgical pathology results were used as the gold standard. We plotted working curves to compare the diagnostic efficacy of CEUS and FNA alone and in combination in the diagnosis of thyroid nodules with halos. The pathological features of the halo were analyzed and the number of patients with cervical lymph node metastases was recorded.

Results: One hundred and sixty patients met the requirements. Benign nodules were mainly characterized by a thin (0.75 ± 0.31 mm) and uniform halo with good integrity, while malignant nodules had a thicker (1.48 ± 0.51 mm) halo with uneven and irregular margins (P < 0.05). The sensitivity and specificity were highest when the cutoff value was 1.09 mm, with 76.08% and 84.29%, respectively. The halos of benign nodules were mostly hyper- or iso-enhanced, whereas the halos of malignant nodules were predominantly hypo-enhanced (P < 0.05). The areas under the curve (AUCs) for CEUS, FNA, and CEUS + FNA were 0.751(95% CI = 0.642-0.841), 0.863(95% CI = 0.767-0.929), and 0.918(95% CI = 0.834-0.967), respectively. Cervical lymph node metastasis occurred in only 13 (11.5%) malignant nodes with halos. The primary pathological components of the halo around malignant nodules were almost reactive hyperplastic fibrous tissue.

Conclusion: The halo surrounding malignant thyroid nodules is thicker, with uneven and irregular margins, and shows hypo-enhancement on CEUS. Combining CEUS with FNA improves the diagnostic efficacy of thyroid nodules with halos. The reactive hyperplastic fibrous halo may be one of the reasons why malignant nodules are less likely to metastasize.