Objective To investigate the application value of computed tomography (CT) examination of lymph node short diameter in evaluating left recurrent laryngeal nerve lymph node metastasis in thoracic esophageal squamous cell carcinoma.

Methods The retrospective and descriptive study was conducted. The clinicopathological data of 628 patients with thoracic esophageal squamous cell carcinoma who were admitted to 2 medical centers (236 cases in the Sun Yat-sen University Cancer Center and 392 cases in the Affiliated Cancer Hospital of Zhengzhou University) from October 2009 to December 2016 were collected. There were 462 males and 166 females, aged from 38 to 85 years, with a median age of 62 years. Observation indicators: (1) operation status, dissection and metastasis of left recurrent laryngeal nerve lymph node; (2) efficacy of CT examination of the left recurrent laryngeal nerve lymph node short diameter in evaluating postoperative lymph node metastasis; (3) determination of the optimal cut-off value; (4) examination results using different diagnostic criteria. Measurement data with skewed distribution were represented as M (range). Count data were described as absolute numbers or percentages. The area under curve (AUC) of receiver operating characteristic curve (ROC) was used to estimate the efficiency of detection methods. The maximum value of Youden index corresponded to the optimal cut-off point.

Results (1) Operation status, dissection and metastasis of left recurrent laryngeal nerve lymph node: among the 628 patients, there were 572 cases undergoing two-field lymph node dissection while 56 cases undergoing three-field lymph node dissection, there were 408 cases undergoing minimally invasive surgery while 220 cases undergoing open surgery. Sixty of 628 patients had left recurrent laryngeal nerve lymph node metastasis. A total of 1 666 left recurrent laryngeal nerve lymph nodes were dissected from the 628 patients, among which 75 were metastatic lymph nodes, with a metastasis rate of 4.502%(75/1 666). (2) Efficacy of CT examination of the left recurrent laryngeal nerve lymph node short diameter in evaluating postoperative lymph node metastasis: the AUC of CT examination of the left recurrent laryngeal nerve lymph node short diameter in predicting postoperative lymph node metastasis was 0.854 (95% confidence interval as 0.792 to 0.916, P<0.05). (3) Determination of the optimal cut-off value: the Youden indices were 0.556, 0.384, 0.258, 0.063 and 0.003 respectively when using 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm as the optimal cut-off value for CT examination of the left recurrent laryngeal nerve lymph node short diameter. The short diameter as 5 mm was the optimal cut-off value for CT examination of the left recurrent laryngeal nerve lymph node short diameter. (4) Examination results using different diagnostic criteria: the sensitivity, specificity, accuracy, positive predictive value, negative predictive value, cases being missed diagnosis were respectively 66.3%, 92.3%, 89.5%, 46.3%, 96.0%, 20 and 5.0%, 99.8%, 90.7%, 75.0%, 90.9%, 57 when using short diameter ≥5 mm or ≥10 mm in CT examination of the left recurrent laryngeal nerve lymph node as the diagnostic criteria for left recurrent laryngeal nerve lymph node metastasis of thoracic esophageal squamous cell carcinoma.

Conclusions CT examination of lymph node short diameter can be used to evaluate left recurrent laryngeal nerve lymph node metastasis in thoracic esophageal squamous cell carcinoma. The sensitivity, specificity and accuracy is preferable when using short diameter ≥5 mm in CT examina-tion of the left recurrent laryngeal nerve lymph node as the diagnostic criteria for left recurrent laryngeal nerve lymph node metastasis of thoracic esophageal squamous cell carcinoma.