The value and practical utility of intraoperative touch imprint cytology of sentinel lymph node(s) in patients with breast cancer: A retrospective cytology-histology correlation study

Objective Intraoperative evaluation of sentinel lymph nodes (SLNs) for patients with breast cancer is widely performed with frozen section (FS), cytology, or a combination of both. Touch imprint cytology (TIC) reportedly has an equivalent sensitivity to FS. We studied its diagnostic utility to detect SLN metastases. Materials and Methods Cases of 367 patients with breast cancer who underwent intraoperative valuation of SLNs (507 LNs) were evaluated. All FS and corresponding TIC slides of SLNs of each case were reviewed microscopically for the presence of metastases of any size. If present, the metastatic focus was measured on the FS. Results Of these 507 SLNs, 82 LNs (16.2%) from 69 women were found to have metastases in the FS and consisted of 5 LNs of isolated tumor cells, 15 of micrometastasis, and 62 of macrometastasis. TIC identified metastases in 69 of these 82 SLNs (sensitivity: 84.1%, specificity: 100%, and accuracy: 97.4%). All macrometastases could be detected by TIC, whereas TIC identified approximately 50% of micrometastases and none of isolated tumor cells. The size detection limit of metastatic foci, defined as the smallest dimension of metastasis detected without false negatives, was 2 mm. The smallest metastatic focus identified was 0.8 mm. Conclusions TIC of SLNs is of great use given its negative predictive value of 100% for identification of macrometastasis in our study. For intraoperative evaluation of SLNs, based on our data, a practical two-step approach is proposed: SLN evaluation should be initially performed by TIC and then proceed to FS histological analysis only when cytologically positive to determine the size of metastatic focus.