Imprint cytology versus frozen section: intraoperative analysis of sentinel lymph nodes in breast cancer

Background: Intraoperative analysis of the sentinel node status in breast cancer adds the benefit of proceeding to axillary dissection at the same time as the primary breast operation, without the need for a second trip to theatre. However, the method of intra­operative analysis must be both rapid and accurate for use in this setting. Methods: A prospective series of 20 consecutive patients in one hospital who underwent sentinel node biopsy was performed. Intraoperative evaluation by imprint cytology and frozen section was compared with the final histopathological results. The time taken for both procedures was recorded. Results: A total of 21 sentinel node procedures was performed. The sentinel node was found in 20 procedures (95%). The average time to perform intraoperative pathological analysis was 17 min (range: 5−35 min). Of the eight positive sentinel nodes, five were positive on imprint cytology alone and five were positive on frozen section alone (62.5% accuracy). The statistical false negative rate was 18.8% and the ‘false reassurance rate’ (patients with an initially negative node that was subsequently positive on formal histology who required a second trip to theatre for axillary dissection) was 37.5%. All patients with a negative sentinel node had a negative axilla. Conclusions: Intraoperative analysis of sentinel lymph nodes in breast cancer can be performed quickly. Imprint cytology and frozen section show comparable accuracy in predicting sentinel node status.