Endoscopic ultrasound guided fine needle aspiration (EUS-FNA) has evolved because of its limitations. Early studies indicated that 5-7 passes were needed during EUS-FNA to ensure adequate diagnostic yield. Because of the need to reduce the number of passes, EUS guided fine tissue acquisition (EUS-TA) has evolved from FNA alone to FNA combined with rapid onsite pathologic evaluation (ROSE), and FNA combined with macroscopic onsite evaluation (MOSE). A recent randomized controlled study showed that EUS-TA with MOSE was comparable to conventional EUS-TA in diagnostic yield but needed fewer passes.
The emergence of personalized medicine has led to the need for histologic diagnosis and bigger specimens. This prompted the development of fine needle biopsy (FNB). A meta-analysis showed that while FNB was equivalent to FNA in diagnostic accuracy/yield, FNB reduced the number of passes needed to obtain diagnostic samples.
In the diagnosis of pancreatic cystic lesions, fluid cytology is known to be insensitive, with a false negative rate of up to 50%. To overcome this limitation, and increase diagnostic yield of cystic lesions, EUS-TA has evolved from fluid aspiration to cystic wall biopsy. The latter could be done with the use EUS-guided microforceps.
In summary, EUS-TA has evolved because of the needs to overcome limitations including the impracticality of doing too many passes, the small sample size of FNA, and the insensitivity of cystic fluid cytology.