Ultrasound-guided fine needle aspiration cytology as an addendum to sentinel lymph node biopsy can perfect the staging strategy in melanoma patients

Background Ultrasound guided fine needle aspiration cytology (US-guided FNAC) can identify microscopic involvement of lymph nodes as in breast cancer and avoid surgical sentinel node (SN). Its utility in melanoma patients is controversial and subject of this study. Methods Between 2001 and 2010 over 1000 stage I/II consecutive melanoma patients prospectively underwent US-FNAC prior to SN biopsy. All patients underwent lymphoscintigraphy prior to US-FNAC. The Berlin US morphology criteria: Peripheral perfusion (PP), loss of central echoes (LCE) and balloon shaped (BS) were registered. FNAC was performed in case of presence of any of these factors. SN tumour burden was measured according to the Rotterdam criteria. All patients underwent SN or lymph node dissection (LND) in case of positive FNAC. Findings Mean/median Breslow thickness was 2.58/1.57 mm. Mean/median follow-up was 56/53 months (1-132). SN positivity rate was 21%. US-FNAC Sensitivity was 71% (US only) and 51% (US-FNAC). Sensitivity of US-FNAC was highest for T4 (76%) and ulcerated melanomas (63%). PP, LCE and BS had sensitivity of 69%, 24% and 24% respectively. Sensitivity of US-FNAC increased with increasing SN tumour burden. PP was an early sign of metastasis (58% in <0.1 mm metastases). Threshold size of a metastasis for FNAC was 0.3 mm. Five-year survival correlated to US-FNAC status (95% in negative and 59% in positive). Interpretation Ultrasound guided FNAC (US-FNAC) according to the Berlin morphology criteria could correctly identify at least half of all tumour positive sentinel nodes, prior to the surgical SN procedure. Peripheral perfusion is an early sign of metastasis, which is very sensitive, but with lower positive predictive value (PPV). It is responsible for the sensitivity of the procedure. Balloon shape is a sign of advanced metastases, with lower sensitivity, but high PPV. US-FNAC sensitivity correlated with increasing T-stage, ulceration of the primary and increasing SN tumour burden. US-FNAC status accurately predicts survival.