Multivariate feature analysis of sonographic findings of metastatic cervical lymph nodes: contribution of blood flow features revealed by power Doppler sonography for predicting metastasis

Abstract

Background and purpose: Sonographic criteria of the lymph node have been found to be good indicators for metastatic lymph nodes. We determined which sonographic features are most predictive of metastasis in cervical lymph nodes among patients with head and neck cancer.

Methods: Gray-scale and power Doppler sonograms were retrospectively analyzed in 133 cervical lymph nodes (57 metastatic and 76 reactive nodes) from 52 patients with head and neck cancer. The gray-scale sonographic features of the presence or absence of hilar echoes, parenchymal echogenicity, and short and long axis lengths as well as the power Doppler features of normal hilar flow and abnormal parenchymal flow were evaluated. Univariate and multivariate logistic regression analyses were conducted to determine the relative value of each sonographic feature.

Results: At univariate analysis, all sonographic features assessed were found to be important. Multivariate analysis, however, suggested that the presence or absence of hilar echoes, increases in short axis length, and the presence of normal hilar flow were the only sonographic features that were predictive of reactive (presence of hilar echoes and hilar flow) and metastatic (increases in short axis length) lymph nodes. Although multivariate analysis did not indicate any significant contribution of the color-flow criteria for predicting metastatic nodes, the color-flow criteria appeared to improve the overall diagnostic accuracy for the less experienced observer.

Conclusion: The sonographic criteria most predictive of metastatic cervical lymph nodes were absent hilar echoes and increases in short axis length, as assessed by logistic regression analysis. Compared with these gray-scale criteria, color-flow criteria had fewer predictive advantages.

fig 1.

Case of a 61-year-old man with squamous cell carcinoma of the hard palate. A, Gray-scale sonogram of a reactive cervical lymph node shows homogeneous and low echogenicity of the parenchyma and normal hilar echoes (arrows). B, Power Doppler sonogram of the same node as that shown in panel A shows a normal reactive hilar blood flow.

fig 2.

Case of a 53-year-old man with squamous cell carcinoma of the hypopharynx. A, Gray-scale sonogram of a metastatic cervical lymph node shows abnormal, heterogeneous echogenicity of the parenchyma. B, Power Doppler sonogram of the same node as that shown in panel A shows abnormal parenchymal blood flow, characteristic of metastasis.

fig 3.

Sonograms of a reactive node from a 54-year-old man with squamous cell carcinoma of the larynx (A) and a metastatic node from 64-year-old man with squamous cell carcinoma of the hypopharynx (B) show a preferential increase in short axis diameter of the metastatic node. A, Gray-scale sonogram shows reactive cervical lymph node with relatively flat shape. Arrows indicate hilum. B, Gray-scale sonogram shows metastatic cervical lymph node. Note that the lymph nodes in panels A and B exhibit similar longitudinal axis lengths, but that the metastatic node in B has a greater short axis length. The metastatic node also shows a focal area of necrosis (arrows).

fig 4.

Case of a 66-year-old man with squamous cell carcinoma of the upper gingiva. This case shows the value of the presence of hilar echoes over that of increased short axis diameter. The presence of normal hilar flow as detected by Doppler sonography is helpful for confirming the presence of normal hilar echoes. A, Gray-scale sonogram of a reactive cervical lymph. The short axis length is increased, suggestive of metastatic node; however, the normal hilar echo is present (arrows). B, Power Doppler sonogram of the same reactive node as that shown in panel A shows a normal hilar flow (arrows).