MOSE FOR EUS-GUIDED PANCREATIC TISSUE ACQUISITION: THE THIRD WAY

Aims To increase FNA performance ROSE and the use of core needles have been extensively analyzed. The aim of this study was to assess the role of the macroscopic on-site evaluation (MOSE) to raise the adequacy of pancreatic FNA.

Methods From our prospectively maintained database we extracted the FNA procedures for solid pancreatic lesions in which the MOSE technique was applied. In our center this method is performed by one endosonographer since 2013, when he attended a formal training by our pathologists to become familiar with the technique of smearing and gross evaluation of the specimens. During EUS, after each 22G/25G needle pass, the endoscopist emptied the needle onto the slides; afterwards he smeared and assessed the slides under oblique white light before fixation. Each endoscopic procedure was carried on, regardless of the number of needle passes, till five slides showed an opaque thin granular or thread-like whitish material; bloody smears were eliminated. The final microscopic adequacy was established from the pathological reports.

Results 221 patients entered the study; the mean size of the target lesions was 33mm. FNA was adequate in 212 cases (95.9%) after a mean of 3.8 needle passes; adequacy with 22G or 25G needles was equal (94.6% vs 97.8%; p=0.31). For lesions < 20mm adequacy was 34/36=94.4%. For procedures with ≤2 needle passes adequacy was 28/30=93.3%.

Conclusions This is the largest series of MOSE application to pancreatic FNA; its single-operator design reduces the bias due to the interobserver variability. This technique, when performed by a trained endosonographer, can get a very high adequacy rate, even for small lesions or after a few needle passes. Given the costs of ROSE and the difficulty to get tissue from small lesions with side-holed histological needles, MOSE represents a simple and cheap third strategy to increase the adequacy of EUS-guided pancreatic tissue acquisition.