Rotterdam Criteria for Sentinel Node (SN) Tumor Burden and the Accuracy of Ultrasound (US) -Guided Fine-Needle Aspiration Cytology (FNAC): Can US-Guided FNAC Replace SN Staging in Patients With Melanoma?

PURPOSE: Sentinel node (SN) status is the most important prognostic factor for overall survival (OS) for patients with stage I/II melanoma, and the role of the SN procedure as a staging procedure has long been established. However, a less invasive procedure, such as ultrasound (US) -guided fine-needle aspiration cytology (FNAC), would be preferred. The aim of this study was to evaluate the accuracy of US-guided FNAC and compare the results with histology after SN surgery was performed in all patients. PATIENTS AND METHODS: Four hundred consecutive patients who underwent lymphoscintigraphy subsequently underwent a US examination before the SN procedure. When the US examination showed a suspicious or malignant pattern, patients underwent an FNAC. Median Breslow thickness was 1.8 mm; mean follow-up was 42 months (range, 4 to 82 months). We considered the US-guided FNAC positive if either US and/or FNAC were positive. If US was suggestive of abnormality, but FNAC was negative, the US-guided FNAC was considered negative. RESULTS: US-guided FNAC identified 51 (65%) of 79 SN metastases. Specificity was 99% (317 of 321), with a positive predictive value of 93% and negative predictive value of 92%. SN-positive identification rate by US-guided FNAC increased from 40% in stage pT1a/b disease to 79% in stage pT4a/b disease. US-guided FNAC detected SN tumors more than 1.0 mm in 86% of cases, SN tumors of 0.1 to 1.0 mm in 46% of cases, and SN tumors less than 0.1 mm in 23% of cases. Estimated 5-year OS rates were 92% for patients with negative US-guided FNAC results and 51% for patients with positive results. CONCLUSION: US-guided FNAC of SNs is highly accurate. Up to 65% of the patients with SN-positive results in our institution could have been spared an SN procedure.