Tissue rinse liquid-based cytology: a feasible tool for the intraoperative pathological evaluation of sentinel lymph nodes in breast cancer patients

Abstract

A unique diagnostic method was designed for the intraoperative pathological evaluation of sentinel lymph nodes (SLNs) in breast cancer patients, and the results were verified with 2 years of experience. Excised lymph nodes were cut into 2-mm-thick slices and rinsed thoroughly in CytoRich Red(®). The sliced tissues were embedded in a paraffin block. Three cytological glass slides of the cells exfoliated in CytoRich Red(®) were prepared by the SurePath(®) liquid-based cytology (LBC) technique. Two slides were stained by the Papanicolaou method, and the remaining slide was immunostained with an anti-keratin antibody. This process is called tissue rinse liquid-based cytology (TRLBC). The results of TRLBC were compared with those of the final pathological diagnoses, including immunostaining with an anti-keratin antibody on paraffin blocks (PB). This study analysed 444 SLNs from 247 consecutive breast cancer patients. It required 35 minutes to complete the intraoperative diagnosis on a single node, and it took an additional 5 minutes per node if more than one node was submitted. When the results of PB were assumed to be the gold standard, the sensitivity and specificity of TRLBC were 81.9% and 96.1%, respectively. TRLBC detected all nodes with macrometastasis and 23 of 24 nodes with micrometastasis. Fifteen false-negative TRLBC results were 'isolated tumour cell clusters' on PB, but there was one with micrometastasis histologically. Four of 14 false-positive TRLBC results were proven to be true positive by supplementary examination using step sectioning of the paraffin blocks of the nodes. TRLBC is a feasible and promising intraoperative cytopathological tool showing a comparable efficacy to PB while still allowing the conventional postoperative histological examination.