Diagnostic criteria of sentinel lymph node micrometastasis or macrometastasis based on tissue rinse liquid-based cytology in gynecological cancer

Objective This study aimed to establish intraoperative diagnostic criteria of sentinel lymph node (SLN) micro-/macrometastasis on the basis of tissue rinse liquid-based cytology (TRLBC) in gynecological cancer. Methods We enrolled 214 patients with gynecological cancer who underwent rapid diagnosis of SLN metastasis on the basis of TRLBC from a total of 490 SLNs. For slides that were classified as positive for atypical cells on cytological inspection, we counted the number of clusters (an atypical cell mass consisted of three or more cells) and the number of single cells (an atypical cell other than clusters). Receiver operating characteristic (ROC) analysis was applied to determine the efficiency of predicting SLN micro-/macrometastasis. Results On cytological inspection, 36 slides were classified as positive for atypical cells, while 21 slides (4.3%) were true positive, 15 (3.1%) were false positive, and 454 (92.6%) were true negative. There were no false negative results in this study. The area under the ROC curve for the number of cluster was superior to that for the number of single cells for distinguishing micro-/macrometastasis from negative/isolated tumor cells (0.86 vs. 0.67, P = 0.032). The optimum cut-off value of the number of clusters was 5 for distinguishing these two categories. Conclusions TRLBC is a highly sensitive alternative for detecting SLN metastasis as a rapid intraoperative diagnosis. Counting the number of atypical cell clusters might be useful for distinguishing micro-/macrometastasis from isolated tumor cells.