Intraoperative evaluation of sentinel lymph nodes for metastatic melanoma by imprint cytology

BACKGROUND. 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. To date, several studies have evaluated the use of intraoperative frozen sectioning to evaluate the SLN in patients with melanoma. The literature pertaining to the use of intraoperative imprint cytology (IIC) to evaluate the SLN in melanoma patients is scant and to the authors' knowledge studies published to date are relatively small. The purpose of the current study was to evaluate the utility of IIC in patients undergoing SLN for melanoma. METHODS. A total of 235 SLN biopsies from 93 patients with malignant melanoma and 3 patients with atypical Spitz nevi were examined by IIC after SLN biopsy using a double indicator technique. The SLNs were bisected and a pair of imprints were made from each hall One imprint from each half was stained with hematoxylin and eosin (H & E) whereas its counterpart was stained with Diff-Quik. Paraffin-embedded permanent sections were examined using multiple H & E stained sections from the SLNs in conjunction with immunohistochemical staining for S-100 and HMB-45 proteins. RESULTS. A total of 235 SLNs were excised from 93 patients (2.5 SLNs per patient). On a per patient basis, metastases were identified in 21 patients (23%) on permanent section evaluation. Of these 21 patients, 8 were detected by IIC (sensitivity of 38%). The negative predictive value was 85%. No false-positive results were identified (specificity of 100%). The positive predictive value was 100%. The overall accuracy of the intraoperative evaluation was 86%. Patients found to have positive SLNs by IIC went on to undergo lymphadenectomy under the same anesthetic. CONCLUSIONS. The sensitivity and specificity of IIC are similar to those of intraoperative frozen-section evaluation. Therefore, IIC appears to be a viable alternative to frozen sectioning when intraoperative evaluation is required. IIC evaluation of SLN makes a single surgical procedure possible for patients with malignant melanoma who are undergoing SLN.