Anatomic Variability of the Upper Mediastinal Lymph Node Level VII.

Abstract

Lymph node level VII, between the sternal notch and the innominate artery, is a frequent site of lymph node metastases in thyroid cancer. The objective of this study was to determine the cranial-caudal dimensions of level VII in patients undergoing central neck dissection for thyroid cancer and its accessibility through a neck incision only. Consecutive patients undergoing central neck dissection for thyroid cancer, with no previous neck dissection, mediastinal or thoracic surgery. The innominate artery was identified and the distance between the sternal notch and the upper border of the artery was measured to the nearest .5mm. The sizes of level VII were compared with respect to age, sex, height, body mass index, type of neck dissection (therapeutic or prophylactic), and the incidence of previous thyroidectomy. One-hundred-one consecutive patients (65 women, 36 men, mean age 44years (range 15-87) underwent prophylactic (n=55) or therapeutic (n=46) bilateral central compartment neck dissection. Level VII was accessible via the horizontal neck incision in all cases. Sizes of level VII ranged from 6cm above the sternal notch to 35mm below the sternal notch, with a mean distance of 3.5mm below the sternal notch. The innominate artery was at the level of the sternal notch in 29 patients, and cranial to the sternal notch in 20 cases. No statistical relationship with age, sex, therapeutic/prophylactic neck dissection, previous surgery, body mass index or height was found. The maximal distance below the sternal notch was 35mm. Level VII did not exist in 49% of patients, and was less than 25mm caudal to the sternal notch in 95% of cases. Distinguishing level VII from level VI in thyroid cancer surgery may not be pertinent, due to the ease of access via a classic horizontal neck incision and the small sizes of level VII in the majority of patients.