A Risk Stratification Model for Metastatic Lymph Nodes of Papillary Thyroid Cancer: A Retrospective Study Based on Sonographic Features

Abstract

Background: Papillary thyroid carcinoma (PTC) has a high probability of cervical lymph node (LN) metastasis. The aim of the study was to develop an ultrasound risk stratification model to standardize the diagnosis of metastatic LNs of PTC.

Methods: Patients with suspicious thyroid nodules who underwent US examination and US guided fine-needle aspiration for cervical LNs were retrospectively collected. Univariate and multivariate logistic regression analyses were performed to assess the independent risk factor of metastatic LNs. According to the OR value of correlated indicators in logistic regression analysis, a risk stratification model was established.

Results: A total of 653 LNs were included. The independent risk factors of metastatic LNs were long-axis diameter/short-axis ≤ 2 (OR=1.644), absence of hilum (OR=1.894), hyperechogenicity (OR=5.375), calcifications (OR=6.201), cystic change (OR=71.818), and abnormal flow (OR=3.811) (P<0.05 for all). The risk stratification model and malignancy rate were as follows: 0-2 points, malignancy rate of 10.61%, low suspicion; 3-5 points, malignancy rate of 50.49%, intermediate suspicion, ≥6 points, malignancy rate of 84.81%, high suspicion. The area under the receiver operating characteristic curve for the model was 0.827 (95% CI 0.795-0.859).

Conclusions: Our established risk stratification model can effectively evaluate metastatic LNs in the patients with suspicious thyroid nodules, and it might provide a new strategy choice for clinical practice.

Keywords: lymph node; metastasis; papillary thyroid carcinoma; risk stratification; ultrasonography.

Figure 1

Flow chart shows selection of study population and diagnoses of lymph nodes.

Figure 2

Ultrasonographic image of lymph nodes. (A) A metastatic lymph node in a 32-year-old man with PTC was classified as low suspicion. The lymph node was located in right level IV and measured 17.7×3.8mm, with echogenic hilum (white arrow) and L/S>2. The total score was 0. (B) A metastatic lymph node in a 39- year-old woman with PTC was classified as intermediate suspicion. The lymph node was located in left III level, and grayscale sonogram demonstrated that the lymph node was measured 14.4×3.5mm with microcalcifications (white arrow) and no echogenic hilum. The total score was 5. (C, D) A suspicious lymph node in a 63-year-old woman with PTC was classified as intermediate suspicion. The cytological result was benign, and follow-up ultrasound was performed. The lymph node was located in right II level. The total score was 3. (C) The grayscale ultrasonographic image showed a hypoechoic lymph node, which was measured 25.2×9.4mm, with echogenic hilum and calcification (white arrow). (D) Color Doppler showed that the lymph node had a hilar vascularity (white arrow). (E, F) A metastatic lymph node in a 33-year-old woman was classified as high suspicion. The lymph node was located in left IV level. The total score was 19. (E) The gray ultrasonographic image showed a hyperechoic lymph node, which was measured 28.2×14.7mm, with a L/S ≤2 shape, absence of hilum, microcalcifications (white arrow), and cystic change (black arrow). (F) Color Doppler showed that the lymph node had a mixed vascularity pattern (black arrow).