<Background/aims> Rapid onsite evaluation (ROSE) of endoscopic ultrasound-guided fine needle aspiration and biopsy (EUS-FNAB) specimens by attending cytopathologists has been demonstrated to improve diagnostic yields of EUS-FNAB. The practice of ROSE, however, varies across EUS programs in Unites States, Europe and other areas of world. The investigators have a plan to perform prospective evaluation of the yield of EUS-FNAB in the absence of ROSE, in which the adequacy of specimens will be assessed by a single endosonographer.

<Methods> All EUS-FNAB procedures will be performed by an experienced endosonographer and the adequacy of specimens obtained during EUS-FNAB will be also assessed by a same endosonographer. A specimen will be considered adequate if there is an adequate number of representative cells from the lesion. Samples considered to be adequate will be then interpreted as malignancy, highly atypical suggestive of malignancy, atypical favor reactive change, or negative for malignancy. Performance characteristics of EUS-FNAB including sensitivity, specificity, and accuracy will be determined by comparing EUS-FNAB results with the final diagnoses of the lesions, based upon the surgical pathology or clinical follow-up of more than 6 months with repeat imagings.

Inclusion Criteria:

• Any patients who will undergo EUS-FNA for the diagnostic evaluation of pancreas lesion

Exclusion Criteria:

• Patients who refuse to undergo EUS-FNA

Any patients who will undergo EUS-FNA for the diagnostic evaluation of pancreas lesion