Selective use of intraoperative touch prep analysis of sentinel nodes in breast cancer.

Imprint cytology (touch prep) is often used for intraoperative examination of sentinel nodes in breast cancer. This allows axillary lymph node dissection (ALND) to be performed immediately for tumor-positive nodes. We evaluated the accuracy of touch prep examination of sentinel nodes and its role in the surgical treatment of breast cancer. We analyzed 169 breast cancer patients who underwent 170 lymphatic mapping procedures with intraoperative touch prep examination. Results from the touch prep were correlated with histopathology and clinical variables. There were 115 true-negative, 35 true-positive, 15 false-negative, and 5 false-positive results. Touch prep had a sensitivity of 70 per cent and specificity of 96 per cent. Positive predictive value, negative predictive value, and diagnostic accuracy were all 88 per cent. The false-negative rate was 30 per cent and correlated with the size of the nodal metastasis and number of involved nodes, but not other patient factors. Touch prep is useful for the evaluation of sentinel nodes in breast cancer, but it has a lower sensitivity than initially reported, particularly in patients with micrometastases. False positive results occur, although they may be reduced after experience with the technique. We recommend that suspicious findings on touch prep should be confirmed by frozen section and that ALND only be performed for histologically documented metastases. We currently perform touch prep only in patients who are at high risk of nodal metastasis or will undergo mastectomy. This improves operative efficiency and limits the impact of false positive and negative results without dramatically increasing the number of patients who require a second surgical procedure.