[398] Evaluation of False Negative Intraoperative Touch Imprint Cytology of Sentinel Lymph Nodes in Breast Cancer Patients

A Mohanty, TC Pereira, Y Liu, MS Cowher, TB Julian, JF Silverman. Allegheny General Hospital, Pittsburgh, PA

Background: Intraoperative imprint cytology (IC) of sentinel lymph nodes (SLNs) helps direct surgeons to proceed with axillary lymph node dissection (ALND). False negative (FN) rates of ICs vary between 10-50% in different series. ALND is delayed in FN IC cases, hence the importance of a correct cytologic diagnosis. We analyzed the factors responsible for FN ICs of SLNs and recommend steps to prevent it.
Design: We retrospectively analyzed 342 breast cancer (BC) patients who underwent SLN biopsies (2003-2006). 310 cases had negative IC results, and of these, 33 patients had positive SLN permanent histology. 3 cytopathologists then reviewed these 33 patients having 40 sets of ICs (one Diff-Quik (DQ) and one Hematoxylin-Eosin (H&E) per SLN). The consensus diagnosis at the time of the review was compared with the corresponding positive histology slides. Parameters evaluated included classifying the FN IC results as interpretive errors, BC subtype, diagnosis rendered by cytopathologist (CP) vs. non-cytopathologist (NCP), sampling errors, adequacy of the IC for interpretation, and correlation with the size of the metastatic SLN foci.
Results: IC results in 29/40 SLNs were confirmed negative upon review, while 11 were interpretive errors. 25 SLNs showed micrometastasis, while 15 showed macrometastasis. 25/33 patients had invasive ductal BC, and 8 had lobular BC. 9/40 FN ICs were reported by CPs, while 31 by NCPs. IC in 2 cases was evaluated to be unsatisfactory due to scantly cellular smears. 2 SLNs were partially replaced by tumor metastasis, but the ICs were negative. In 11 SLNs categorized as interpretive errors, the tumor cells were identified in 7 DQ and in all 11 H&E cytologic preps.
Conclusions: Interpretive errors were more common when examination was done by NCPs emphasizing the importance of cytolopathologist's consultation in difficult and negative cases. ICs were more often negative in SLNs with micrometastasis than with macrometastasis, which probably reflects touch preparation sampling. Two SLNs with large foci of tumor metastasis were found negative on IC, underscoring the importance of gross examination of lymph nodes. Poor preparation technique of IC slides provided insufficient material for cytologic examination contributing to FN SLN interpretation. Tumor cells were identified more frequently on H&E stained IC slides emphasizing the importance of nuclear detail in cytologic diagnosis.
Category: Cytopathology

Monday, March 9, 2009 9:30 AM

Poster Session I Stowell-Orbison/Autopsy Award # 66, Monday Morning