Lateral cervical lymph node metastases in papillary thyroid cancer: a systematic review of imaging-guided and prophylactic removal of the lateral compartment

Background Papillary thyroid cancer (PTC) is a common endocrine cancer and frequently presents with lymph node (LN) metastases. The frequency of LN metastases in the lateral compartment and their surgical removal are poorly defined. There are no prospective randomised controlled trials addressing an eventual outcome difference relating to the extent of the initial surgical approach. The aim of this study was to define the extent of lateral LN involvement and the role of imaging in identification of these metastatic LN. Design and Methods A systematic review of studies of patients with PTC undergoing either prophylactic or therapeutic lymphadenectomy of the lateral cervical compartment. Studies involving imaging modalities in the detection of lateral cervical LNs in PTC were also analysed. Results Systematic review on the frequency of lateral LN metastases and their detection using various imaging tools identified 19 studies containing data on 5587 patients undergoing prophylactic or imaging-guided removal of the lateral compartment. Imaging-guided surgery retrieved cancerous lateral LNs in 446/3178 or 14% of eligible patients, whilst prophylactic lateral neck dissection yielded histopathological proof of cancer in 1177/204 or 57.5% of patients. The frequency of lateral compartment metastases increased with T stage. The sensitivity of ultrasound and CT was poor as low as 27% when accurately calculated. Conclusion Metastatic cervical LNs were found in more than half of patients when prophylactic lateral LN dissection was performed. Use of conventional imaging for the selection of the surgical approach to the lateral cervical compartment may commonly identify stage N1a instead of N1b and thus lead to false stage assignment as stage III rather than stage IV, concealing the severe prognostic implications of this stage progression in individual patients.