Post written by Kosuke Okuwaki, MD, PhD, from the Department of Gastroenterology, Kitasato University School of Medicine, Kanagawa, Japan.

The primary aim of this prospective exploratory study was to use stereomicroscopy to estimate the stereomicroscopically visible white core (SVWC) cutoff length required for the pathological diagnosis of samples obtained using 22-gauge needles.

Rapid on-site cytologic evaluation (ROSE) during endoscopic ultrasound fine-needle aspiration biopsy (EUS-FNAB) may improve accuracy of pathological analyses. However, ROSE is not feasible at all institutions where EUS-FNAB is performed. If the diagnosis of EUS-FNAB using index of SVWC cutoff lengths improved significantly, this may be useful for endoscopists, particularly where ROSE is unavailable.

From the ROC curves calculated for the SVWC length with respect to the final diagnosis, the cutoff length was 11 mm. For pancreatic neoplasms (PNs), the cutoff length was 11 mm and for subepithelial lesions (SELs) it was 3.5 mm. The sensitivities according to these cutoff lengths (per-pass analyses) in the entire cohort, PNs, and SELs were 91.4%, 87.6%, and 98.8%, respectively. In conclusion, we determined that the diagnostic results were significantly improved when the cutoff lengths for SVWCs obtained by EUS-FNAB using 22-gauge needles were ≥11 mm. These new indices may be particularly useful for endoscopists performing EUS-FNAB at institutions that are not adequately equipped for ROSE.

The sample isolation process by stereomicroscopy (SIPS), we newly devised, enabled more reliable collections of white samples under stereomicroscopy in this study. Additionally, lining up the white samples on filter paper may have enabled the preparation of higher-quality FFPE specimens containing a large number of tumor cells in each tissue sample slice.

Figure 1. Sample isolation processing by stereomicroscopy. A, The sample in the puncture needle is extruded onto a petri dish initially by compressing the air in the syringe, and then using a stylet. B, The residual cellular components in the puncture needle are extruded into a different vessel using physiologic saline. C, The worm-like tissue component in the petri dish is immersed in 10% neutral buffered formalin solution in a second previously prepared petri dish. The liquid component remaining after extruding the worm-like tissue component is mixed with the liquid in the vessel from step 2 to send for cytological examination. D, The tissue component in the petri dish is being examined under a stereomicroscope (×30); white and red samples have been dissected using injection needles. The SVWCs are measured using a scale on the microscope monitor screen. E, The white and red samples are closely aligned on separate filter papers, placed in vessels containing 10% neutral buffered formalin to send for pathological analyses.

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