Intraoperative Sentinel Lymph Node Imprint Cytology Diagnosis in Breast Cancer Patients by General Surgical Pathologists: A Single-Institution Experience of 4327 Cases.

Context: Sentinel lymph node (SLN) biopsy is the standard of care for breast cancer (BC) patient staging. The axillary node status can be evaluated by frozen section (FS) or imprint cytology (IC). Despite the major disadvantages of tissue loss and freezing artifact in FS, many pathologists consider SLN IC a more difficult task requiring special expertise and prefer FS to IC. Aims: To conduct a large cohort study to evaluate the results of intraoperative SLN IC, compare them with those of FS and permanent section (PS), and determine the best method for general pathologists. Settings and Design: A very large cohort study with many pathologists engaged was designed and the diagnostic results were compared. Materials and Methods: With 12 pathologists engaged, we conducted the largest patient cohort study of SLN IC to date, including 4,327 consecutive BC patients undergoing SLN biopsy during the past 15 years. The touch imprints were stained using three different methods and evaluated. The PS was used as the gold standard for evaluation. Statistical Analysis: The false positivity, false negativity, accuracy, sensitivity, and specificity of the IC and FS for each pathologist were evaluated and compared. Results: Our results showed an overall sensitivity of 82.7%, specificity of 99.3%, and an accuracy rate of 95.9% for SLN IC, which were comparable to those of FS. The accuracy rate did not correlate with the length of working experience and the staining method. Conclusions: Intraoperative hematoxylin and eosin (H&E)-stained IC preparation was found to be the best SLN examination method for general pathologists.