PURPOSE We have shown that ultrasound (US) -guided fine needle aspiration cytology (FNAC) can accurately identify the sentinel node (SN). Moreover, US-guided FNAC before the surgical SN procedure could identify up to 65% of all SN metastases. Herein we analyzed in detail the different US morphologic patterns of SN metastases. PATIENTS AND METHODS From July 2001 to December 2007, a total of 650 patients with melanoma scheduled for sentinel lymph node dissection were examined. We present the first 400 with sufficient follow-up (mean 40, median 39 months). Several morphologic characteristics were scored. In case of suspicious/clearly malignant US patterns a FNAC was performed. The final histology was considered the gold standard. Results Median Breslow was 1.8 mm. The sensitivity and positive predictive value of the most important factors were: peripheral perfusion (PP) present (77% and 52%, respectively), loss of central echoes (LCE; 60% and 65% respectively), and balloon shape (BS; 30% and 96% respectively). Together these factors have a sensitivity of 82% and PPV of 52% (P < .001). PP identified more patients with lower volume disease. PP and combined BS and LCE were independent prognostic factors for survival (hazard ratio, 2.19; P < .015; and hazard ratio, 5.50; P < .001, respectively). CONCLUSION Preoperative US and FNAC can identify 65% of SN metastases and thus reduce the need for surgical SN procedures. Peripheral perfusion is an early sign of involvement and of crucial importance to achieve a high identification rate. Balloon shape and loss of central echoes are late signs of metastases. We recommend US evaluation to identify those patients, who can directly proceed to a complete lymph node dissection after a positive US-guided FNAC of the SN.

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.