Patients with breast cancer now frequently undergo axillary ultrasound and core biopsy (CB) in an attempt to reduce the number of unnecessary sentinel lymph node (SLN) biopsies. This study aimed to establish the frequency of successful targeting of the SLN by ultrasound guided biopsy. A total of 137 patients had axillary ultrasound of which 121 underwent CB. 73 (60%) patients proceeded to SLN after negative CB. All SLNs were examined for evidence of metastases and previous CB. Of the 73 patients, 51 had no evidence of malignancy in the SLN (true negative = 70%). However nodal deposits were found in the remaining 22 patients, representing a false negative rate for CB of 30%. Overall histopathological evidence of previous CB was identified in 47 (64%) of 73 patients undergoing SLN biopsy. The reason for false negative findings in the 22 (30%) patients was failure to sample the sentinel lymph node in 10 (45%) and failure to sample the metastatic disease in the sentinel node in 11 (55%). This study suggests that both better methods of identifying the sentinel lymph node and more adequate sampling are required.
