Initial Ultrasound Criteria for the Diagnosis of Cervical Lymph Node Metastases from Papillary Thyroid Cancer

Abstract

Introduction: Cervical lymph node metastases from papillary thyroid cancer were classified into three categories according to ultrasound: 1) Metastases were not visible on ultrasound; 2) Metastases met initial criteria for the diagnosis; 3) Metastases met typical criteria for the diagnosis. Purpose: To develop initial ultrasound criteria for the diagnosis of cervical lymph node metastases from papillary thyroid cancer. Material and methods: We studied three groups of cervical lymph nodes in patients with papillary thyroid cancer. The first group consisted of 4307 lymph nodes that were not visible on ultrasound. However, in some of them histology revealed a metastasis. The second lymph node group consisted of 242 metastases, and the third one comprised 17 metastases causing first signs. Ultrasound imaging was performed by use of standard ultrasound machines that are widely used in clinical practice. The presence of metastases in the three groups was confirmed by histology and cytology. Results: According to histological data, metastases were present in 961 (22.3 %) of 4307 cervical lymph nodes of level VI located in the fatty tissue and removed for disease prevention. These lymph nodes were missed on ultrasound, so that metastases remained undetected. Typical criteria for the diagnosis of metastases were: an additional space-occupying lesion in the fatty tissue of the neck, local fat deformation, depth/width ratio over 0.5, no differentiation between the cortical and cerebral layers, predominance of the tissue nature, avascularity, calcifications. Cervical lymph nodes with extranodal extension showed some changes in the shape and outlines, metastatic spread to the adjacent fatty tissue, muscles and vessels. Initial sonographic features that helped to identify a metastasis included microcalcifications and an additional nodal space-occupying lesion occupying a part of the cortical and cerebral layers and being seen as the hyperechoic tissue or a cavity with fluid, or as a mixture of the hyperechoic tissue with fluid. The space-occupying lesion was round or ovoid in shape. There was no extranodal extension of early metastases. The space-occupying lesion was 0.5–0.7 cm in size. Conclusion: Ultrasound can detect metastases that cause first signs. Besides, it helps guide biopsies.