Intraoperative Assessment of Sentinel Lymph Nodes in Patients with Breast Carcinoma: Accuracy of Rapid Imprint Cytology Compared with Definitive Histologic Workup

Background: As sentinel lymph node biopsy (SNB) becomes a new surgical standard in the treatment of patients with breast carcinoma, there is an emergent need for a fast and accurate method with which to assess the SN intraoperatively, so a decision can be made regarding whether to perform axillary lymph node dissection during primary surgery. In the current study, the authors performed a prospective investigation of the relative merits of imprint cytology for that purpose.

Methods: Seventy-six patients with T1-T2 breast carcinoma were included after undergoing successful SNB. SNs were freshly sectioned at 2-mm intervals and imprint smears were obtained from all cut surfaces. The smears were examined using a rapid May-Grünwald-Giemsa stain variation, and the SNs were judged to be positive or negative for metastases. SNs later were submitted for paraffin embedding and serial sectioning. Both hematoxylin and eosin stained and cytokeratin (CK) immunostained sections were examined. The postoperative evaluation of the SNs was taken as the gold standard.

Results: Intraoperative cytology showed a sensitivity of 67.7%, a specificity of 100%, an accuracy of 86.8%, and a negative predictive value of 81.8%. The majority of false-negative cases (8 of 10 cases) were due to micrometastasis in the SNs that were discovered only after exhaustive examination with serial sectioning and CK immunostaining.

Conclusions: The results of the current study demonstrate that the accuracy of imprint cytology is high enough to warrant its use for intraoperative SN assessment. If the findings are negative, axillary lymph node dissection can be omitted. Only a few patients with SN micrometastasis may require reoperation.