Intraoperative Evaluation of Sentinel Lymph Nodes for Metastatic Melanoma by Imprint Cytology

Abstract

Sentinel lymph node biopsy (SLN) has revolutionized nodal staging. Accurate intraoperative evaluation of SLN permits a single procedure, with lymphadenectomy being performed during the initial operative procedure when the SLN is positive. There is a paucity of literature on intraoperative imprint cytology (IIC) evaluation of the SLN in melanoma. The purpose of this article is to present an update to our experience with IIC for SLN in melanoma. Melanoma patients had SLNs examined by IIC. SLNs were bisected, and imprints were made from each half. Imprints were stained with hematoxylin and eosin and with Diff-Quik. Paraffin-embedded sections were examined with multiple hematoxylin and eosin-stained sections from the SLNs in conjunction with immunohistochemical staining for S-100, Melan-A, and HMB-45 proteins. Metastases were identified in 40 (17%) of 229 patients. Of these, 13 patients were detected by IIC (sensitivity, 33%). The negative predictive value was 88%. No false-positive results were identified (specificity, 100%). The positive predictive value was 100%. The accuracy of IIC was 78%. The sensitivity for detecting macrometastases (>2 mm) was better than that for detecting micrometastases (< or =2 mm): 62% vs. 16% (P < .01). Patients with positive SLNs by IIC had lymphadenectomy under the same anesthetic. A total of 533 nonsentinel lymph nodes were identified in 42 patients. Only two patients (8%) had positive nonsentinel lymph nodes after a negative IIC. IIC is a viable alternative to frozen sectioning when intraoperative evaluation is desired. IIC is significantly more sensitive for macrometastases. IIC evaluation of SLNs in melanoma makes a single operative procedure possible for a significant proportion of patients with regional nodal metastases.