To explore the relationship between axillary arch and the position of sentinel lymph node.

A total of 386 breast cancer patients who underwent sentinel lymph node biopsy by the same medical team in the Department of Breast Surgery, Southwest Hospital, Army Medical University from January 2013 to October 2017 were enrolled in the retrospective study. In these patients, we investigated the existence of axillary arch and the relative position of sentinel lymph nodes. The influence of tumor size, lymph node metastasis, operation methods, visualization of sentinel lymph nodes and axillary arch on the position of the sentinel lymph node was analyzed by χ² test.

Axillary arch was found in 65 cases, accounting for 16.8% of all 386 patients. Another 321 cases (83.2%) had no axillary arch. The tumor size, lymph node metastasis, breast operation, axillary operation and visualization of sentinel lymph nodes presented no significant influence on the relative position of sentinel lymph nodes (χ²=0.385, 0.011, 0.370, 0.011, 0.002; P=0.535, 0.918, 0.543, 0.918, 0.966). Among 321 patients without axillary arch, sentinel lymph nodes were located in the loose fat layer between thoracodorsal blood vessels and chest wall (regular position) in 302 cases (94.1%), and in dense fat layer around axillary arch, i. e., the junction of the latissimus dorsi and axillary vein (irregular position) in other 19 cases (5.9%). Among 65 patients with axillary arch, 45 (69.2%, 45/65) patients had sentinel lymph nodes in the regular position and 20 (30.8%, 20/65) in the irregular position. The proportion of the patients with sentinel lymph nodes in the regular position in the patients with axillary arch was significantly higher than that in the irregular position (χ²=36.765, P<0.001). In addition, among the 65 patients with axillary arch, preoperative CT images showed axillary arch in 59 patients (90.8%); among 321 patients without axillary arch, no axillary arch were indicated in preoperative CT. In this study, the accuracy of preoperative CT for the diagnosis of axillary arch was 98.4% (380/386), the sensitivity 90.7% (59/65), and the specificity 100% (321/321).

The existence of the axillary arch has the impact on the relative position of sentinel lymph nodes. For the patients with axillary arch, the sentinel lymph nodes are likely to be found in dense fat layer around axillary arch, i. e., the junction of the latissimus dorsi and axillary vein.