Endoscopic Ultrasound-Guided Tissue Acquisition: Techniques and Challenges.

Endoscopic ultrasound-guided fine needle aspiration (EUS FNA) has made pathological diagnosis of pancreatic neoplasms, diseases involving lymph nodes at various mediastinal and abdominal sites, gastrointestinal submucosal lesions, perirectal lesions, adrenal lesions, and mediastinal masses easy. EUS-guided FNA is a multistep procedure that involves assessment of proper clinical indication, correct selection of FNA needles, and adoption of evidence-based techniques for tissue sampling. EUS FNA is done by needles that are available in different sizes, mainly 25, 22, and 19-gauge needle. The need of onsite cytopathologist, dependence on histology/core biopsy occasionally to get a diagnosis, and inability to reliably assess for molecular markers are important limitations of EUS FNA. EUS-guided fine needle biopsy (FNB) that samples the core of tissue is an exciting new development in the field of diagnostic EUS. FNB needles are expensive than FNA needles, and although the initial results are encouraging, more studies with robust evidence proving their superiority beyond any doubt are needed before they can be widely used.