Introduction Endoscopic ultrasound (EUS) provides tissue sampling from solid and cystic upper gastrointestinal and pancreatic lesions. After a critical multidisciplinary review in 2012, our service identified a need to improve acquisition rates. The cytopathology department was not in a position to provide rapid on-site evaluation (ROSE). We therefore introduced an on-site tissue separation (OTS) technique and submitted separate cytology and core biopsy samples to the laboratory for each needle pass.
Method This is a retrospective review of the impact of OTS on improving tissue acquisition. Samples of all solid lesions underwent OTS. Briefly, the fine needle aspiration (FNA) sample is expressed onto a clean glass slide and solid material is separated out under direct vision for histology. The liquid material remaining on the slide is prepared into a thin film and dried. It is subsequently rehydrated in the cytology department and undergoes standard staining procedures. The solid histology samples undergo standard processing techniques as for core biopsy. All of the liquid material on the slide after separation would have been lost to pathology analysis if FNA material had been directly expressed into a specimen container, as occurred previously. Therefore, in this study, the solid histopathology sample pick up rates are taken as the diagnostic rates at our centre without OTS. Our trust provides a specialist cytologist service and the two samples are reported separately. 22G or 25G needles were used and an average of three passes were performed (range 2–4).
Results All patients who underwent EUS from 2013 to 2016 were included. A total of 557 procedures were performed by a single operator. Of these, 129 had an FNA and biopsy. Cystic lesions have been excluded. The results are summarised in the table below:
Conclusion OTS provided a technique to analyse material that would otherwise have been lost. This is the fine material that separates out from the solid material when the samples are in formaldehyde transport media. Our technique appears to significantly increase diagnostic rates for pancreatic mass lesions and lymph node masses. Although significance is not reached for submucosal lesions and mediastinal mass lesions, it is notable that OTS increases the rate of diagnosis across the board without additional needle passes. OTS can be an option in EUS units that do not have access to rapid on-site examination (ROSE) and wish to increase tissue acquisition rates.
Disclosure of Interest None Declared
- Endoscopic Ultrasound