False-negative ultrasound-guided fine-needle aspiration of axillary lymph nodes in breast cancer patients

Introduction The purpose of this study was to clarify the clinicopathological features of patients with false-negative fine needle aspiration cytology (FNAC) and to determine the factors associated with negative FNAC. Methods Patients with negative FNAC from January 2010 to December 2019 were included. The patients with positive sentinel nodes (SN) were divided into two groups: micrometastasis (<= 2 mm) group and macrometastasis (>2 mm) group. The clinicopathological characteristics were compared between the two groups using the chi(2)test. Results A total of 165 patients with negative FNAC were included; 52 (31.5%) had positive SNs. Of the 52 patients, 13 (25%) had micrometastasis and the remaining 39 (75%) had macrometastasis. Of the 113 patients with negative SNs, none had metastases found in non-SNs. No significant differences were observed in age, cT stage or subtype, and preoperative ultrasound findings between the two groups. Conclusions The false-negative rate of FNAC was high (31.5%). Micrometastatic disease was seen in patients with negative FNAC, and this might be the cause of false-negative FNAC results.