Role of ultrasound-guided fine-needle aspiration in melanoma
Ultrasound-guided fine-needle aspiration cytology (US-FNAC) can detect early lymph node metastases in many malignant conditions aiding early diagnosis. This procedure is now successfully being used in patients with melanoma for the detection of stage III disease by high-resolution ultrasound and FNAC.
Primary melanomas can metastasize linearly and spread to distant organs by draining into adjacent lymph nodes, or, hematogeneously, and then develop distant metastases. It has been suggested that linear spread is usually associated with early detection. FNAC is considered of utmost value in early detection of stage III melanoma. Surgical intervention at this stage can increase overall survival rates. FNAC is a relatively minimally invasive procedure with a sensitivity and specificity of 96.3% and 98.9% respectively.
A meta-analysis of 74 studies (n=10,258) confirmed that in melanoma patients, ultrasound was superior for the primary staging of lymph nodes with a sensitivity of 60% and a specificity of 97%, whereas PET-CT was superior for the detection of distant visceral metastases with a sensitivity of 80% and a specificity of 87%.
Ultrasound-guided fine-needle aspiration cytology is performed under sonographic guidance to suspect lesions with 0.4–0.45 mm external diameter needles (26–27 gauge) on a ‘binder valve’ that helps in aspiration of material. The procedure is repeated 3-5 times to ensure adequate aspirates to transfer on to slides for staining.
US-FNAC has demonstrated efficacy in the detection of sentinel nodes and metastatic involvement with a sensitivity of 82% and a specificity of 72%. Patients could benefit by this procedure all through their follow-up. Additional advantage of US-FNAC is that patients may not need extra sentinel node biopsy surgical procedure, reducing morbidity and costs. In Germany and The Netherlands, ultrasound of the primary tumor region, the lymphatic track and regional lymph node basins are part of routine follow-up for all melanoma patients stage ≥IB. It is recommended that patients with malignant melanoma IB–IIB are followed twice a year for 3 years by ultrasound, stages IIC–IV every 3 months for 3 years and every 6 months in the 4–5th year after primary diagnosis (without progression).
It is important that proper training is provided to healthcare professionals for adopting US-FNAC. This diagnostic procedure can be a valuable tool for the early detection and improving survival rates in patients with melanoma.
Source
Schäfer G, Eggermont AMM, Voit CA. Methodology and Clinical Utility of Ultrasound-guided Fine-needle Aspiration Cytology of Lymph Nodes in Melanoma Patients. Expert Rev Dermatol. 2013;8(2):145-153.