Endoscopic ultrasound (EUS) changed the diagnosis and management of gastrointestinal (GI) and adjacent organ diseases. The EUS needle plays a important role in tissue acquisition for cytological and histological evaluation during those tools. Over the past three decades, contined innovations in needle design, gauge size, and functionality have enhanced diagnostic accuracy, safety, and clinical applicability.
EUS needles are primarily used for two purposes:
Fine Needle Aspiration (FNA): FNA is designed for cytological evaluation, especially useful in pancreatic masses, lymph nodes, and submucosal lesions.
Fine Needle Biopsy (FNB): FNB is engineered to preserve tissue architecture, facilitating histological analysis and immunohistochemistry.
Beveled needles, Franseen-tip, Fork-tip, and reverse bevel are some common designs. Gauges normally from 19G to 25G, with balancing flexibility, tissue yield, and safety. For instance, 25G needles provide improved maneuverability and reduced complication risk, while 19G needles deliver superior histological core samples but with high requirements for doctors' operation
Advantages of EUS needle
1. Minimally invasive: Provides tissue samples without the open surgery.
2. With high diagnostic yield: By some recent meta-analyses report that diagnostic sensitivity between 85–90% for malignancy detection in pancreatic lesions.
3. Safe: The complication rates remain low (<2%), mainly consisting of mild bleeding, infection, or pancreatitis.
4. Versatility: It applied to lesions in the pancreas, mediastinum, liver, lymph nodes, and subepithelial GI tumors.
However, EUS needle technology also face challenges:
1. Sample adequacy: FNA sometimes yields insufficient tissue, necessitating repeat procedures.
2. Operator dependence: Success is highly influenced by endoscopist expertise and availability of rapid on-site evaluation (ROSE).
3. Technical difficulty: Large-caliber needles may be difficult to maneuver in angulated positions within the GI tract.
4. Cost considerations: Advanced biopsy needles increase procedural costs, which may limit adoption in resource-constrained settings.
Clinical Evidence and Case Reports
Numerous international studies and case series confirm the clinical impact of EUS-guided tissue sampling:
Pancreatic lesions: A multicenter trial (Bang et al., Gastroenterology, 2018) demonstrated superior histological yield with Franseen-tip needles compared to traditional FNA.
Subepithelial tumors: Case series show that EUS-FNB enables immunohistochemical profiling, which is very important for gastrointestinal stromal tumor (GIST) diagnosis.
Lymphadenopathy: Large cohort studies confirm >85% accuracy in distinguishing malignant from benign lymph nodes.
Emerging therapeutic applications: Reports highlight EUS-guided injection, fiducial placement, and cyst drainage using specialized needles.
Current Trends
Shift from FNA to FNB: Biopsy needles with enhanced tissue acquisition are increasingly preferred, as they reduce the need for repeat sampling and allow for precision oncology applications.
Integration with molecular testing: EUS-FNB samples now support next-generation sequencing (NGS), enabling personalized cancer therapy.
Needle innovation: Flexible alloy shafts, echogenic markings, and ergonomic handles improve visibility and control.
Future Perspectives
The future of EUS needle technology is likely to be shaped by three key developments:
With multiple needles: sufficient tissue can be extracted for analysis at one time.
Personalized medicine: Demand for high-quality tissue will drive the adoption of biopsy needles that support molecular profiling.
Therapeutic EUS: Needles may can evolve into multifunctional devices enabling local drug delivery, ablation, or stem cell transplantation.
AI: Integration of AI-assisted imaging may enhance targeting accuracy and reduce operator variability.
