Intraoperative touch imprint cytological analysis of sentinel lymph nodes for the presence of metastases in malignant melanoma.

Objective: Sentinel lymph node (SLN) biopsy has revolutionized lymph node staging in patients with malignant melanoma. Intraoperative evaluation is a new addition to the SLN procedure that allows for a one-step regional lymph node dissection to be performed when the SLN biopsy findings are positive. The discriminatory immunostaining pattern with the S-100 and HMB45 monoclonal antibodies allows intraoperative immunocytochemical evaluation of imprint smears of SLNs for melanoma metastases.

Methods: One hundred twenty eight SLNs from a cohort of 52 patient-cases that had been identified using sulfur colloid as a radioactive tracer and isosulfan blue were bisected for rapid Diff-Quick stained touch preparations. Intraopera-tive evaluation of sentinel node status by imprint cytology was correlated with the histopathological results of permanent sections. Tumor-negative nodes in routine paraffin sections were further investigated with the employment of the S-100 and HMB45 antibodies.

Results: Thirty-six of all SLNs harbored metastases in paraffin sections, from which 32 were identified by imprint cytology (sensitivity 88.8%). Three SLNs were positive by imprint cytology and negative by histopathology of paraffin sections. Comparison of the results of the touch preparations with the final histopathology (hematoxylin-eosin and S-100/ HMB45 stains) demonstrated a sensitivity of 83.3% and a negative predictive value of 92.5%. The specificity and positive predictive value were 100% respectively.

Conclusions: Touch imprint cytology is potentially useful for intraoperative evaluation of SLNs in malignant melanoma patients. Results can be improved if the surface sampled is appropriately enlarged and a rapid immunohistochemical S-100/HMB45 stain on the imprints is utilized.