Analysis of the Relevance of the Ultrasonographic Features of Papillary Thyroid Carcinoma and Cervical Lymph Node Metastasis on Conventional and Contrast-Enhanced Ultrasonography

Abstract

Background: Preoperative prediction of lymph node metastases has a major impact on prognosis and recurrence for patients with papillary thyroid carcinoma (PTC). Thyroid ultrasonography is the preferred inspection to guide the appropriate diagnostic procedure.

Purpose: To investigate the relationship between PTC and cervical lymph node metastasis (CLNM, including central and lateral LNM) using both conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS).

Material and methods: Our study retrospectively analyzed 379 patients diagnosed with PTC confirmed by surgical pathology at our hospital who underwent US and CEUS examinations from October 2016 to March 2021. Individuals were divided into two groups: the lymph node metastasis group and the nonmetastasis group. The relationship between US and CEUS characteristics of PTC and CLNM was analyzed. Univariate and multivariable logistic regression methods were used to identify the high-risk factors and established a nomogram to predict CLNM in PTC. Furthermore, we explore the frequency of CLNM at each nodal level in PTC patients.

Results: Univariate analysis indicated that there were significant differences in gender, age, tumor size, microcalcification, contact with the adjacent capsule, multifocality, capsule integrity and enhancement patterns in CEUS between the lymph node metastasis group and the nonmetastasis group (all P<0.05). Multivariate regression analysis showed that tumor size ≥1 cm, age ≤45 years, multifocality, and contact range of the adjacent capsule >50% were independent risk factors for CLNM in PTC, which determined the nomogram. The diagnostic model had an area under the curve (AUC) of 0.756 (95% confidence interval, 0.707-0.805). And calibration plot analysis shown that clinical utility of the nomogram. In 162 PTC patients, the metastatic rates of cervical lymph nodes at levels I-VI were 1.9%, 15.4%, 35.2%, 34.6%, 15.4%, 82.1%, and the difference was statistically significant (P<0.001).

Conclusion: Our study indicated that the characteristics of PTC on ultrasonography and CEUS can be used to predict CLNM as a useful tool. Preoperative analysis of ultrasonographical features has important value for predicting CLNM in PTCs. The risk of CLNM is greater when tumor size ≥1 cm, age ≤45 years, multifocality, contact range of the adjacent capsule >50% are present.

Keywords: cervical lymph node metastasis; contrast-enhanced ultrasound (CEUS); conventional ultrasound; nomogram; papillary thyroid carcinoma (PTC).

Figure 1

A 39-year-old woman with PTC. (A) Preoperative ultrasound images showing that the size of the tumor was approximately 3.85*3.27*2.01 cm in the right lobe, and the boundary was ill-defined, with microcalcifications. (B) Transverse sonogram showing that the contact range with the capsule was approximately >50%. (C) CEUS showing heterogeneous hyperenhancement in the nodule with interrupted thyroid capsule integrity (no enhancement area). (D) Lymph nodes were metastatic in levels III-IV of the right neck with the normal structures disappearing. (E) Surgical pathology confirming PTC (HE, hematoxylin-eosin, original magnification, ×40). (F) Surgical pathology confirming cervical lymph node metastasis from PTC (hematoxylin-eosin, original magnification, ×40).

Figure 2

A 36-year-old woman with PTC. (A) Preoperative ultrasound images showing that the size of the tumor was approximately 1.81*1.30*1.09 cm in the left lobe, and microcalcification was detected. (B) Transverse sonogram showing that the contact range with the capsule was >50%. (C) CEUS showing hyperenhancement of the whole nodule. (D) Confirmation by surgical pathology as CLNM in ipsilateral level VI (HE, original magnification, ×100).

Figure 3

A 67-year-old woman with PTC. (A) Preoperative ultrasound images showing that the size of the tumor was approximately 1.2*1.0*1.3 cm in the left lobe, the margin was irregular, taller than wide, and calcification was detected. (B) Transverse sonogram showing that the contact range with the capsule was approximately 25%-50%. (C) CEUS showing heterogeneous hypoenhancement in the nodule. (D) Metastatic lymph node showing that the normal structure disappeared, presenting cystic changes. (E) Surgical pathology confirming PTC (HE, original magnification, ×100). (F) Surgical pathology confirming cervical lymph node metastasis from PTC, (HE, original magnification, ×100).

Figure 4

A 42-year-old woman with PTC. (A) Preoperative ultrasound images showing that the size of the tumor was approximately 1.00*0.77*1.03 cm in the right lobe with hypoechogenicity, an irregular margin, a poorly defined boundary and a taller-than-wide shape. (B) Transverse sonogram showing that the contact range with the capsule was approximately 25%-50%. (C) CEUS showing heterogeneous hypoenhancement in the nodule. (D) Metastatic lymph node showing that the normal structure disappeared, and microcalcification was detected inside. (E) Surgical specimen confirming PTC (HE, original magnification, ×100). (F) Surgical specimen confirming cervical lymph node metastasis from PTC (HE, original magnification, ×100).

Figure 5

(A) Nomogram for predicting CLNM in PTC patients based on four risk factors. (B) The ROC curve and AUC of the nomogram; ROC, receiver operating characteristics. (C) Calibration plots of nomogram for predicting CLNM (internal validation set).