['Novel chemotherapy regimens now provide the opportunity for "personalized" care in pancreatic cancer. Little is known about our ability to procure adequate cells for theranostic studies using standard ultrasound-guided fine-needle aspirations and cytologic techniques.', 'To assess cellularity of cytology material in patients with solid pancreatic lesions.', 'One hundred sixty-nine endoscopic ultrasound-guided fine-needle aspirations with positive diagnoses of solid epithelial pancreatic neoplasms were evaluated for smear and cell block cellularity. Cellularity was scored on a scale of 1 to 4; scores of 3 or 4 (>100 cells) were deemed adequate for ancillary studies. Clinicopathologic variables were recorded. A 3-month prospective analysis was also performed using a new collection algorithm.', 'Only 12.4% (21 of 169) of the positive cases had a cell block cellularity score that was adequate for theranostic studies. This score was not associated with on-site evaluation, needle gauge, or number of passes. Adenocarcinoma was the most common diagnosis (88%) but yielded fewer adequate cell blocks, P = .006. Cellularity showed correlation with endoscopists, P = .04. Tumor size and fibrosis score of resected tumors tended to correlate with cellularity, but only larger size in endocrine tumors was significantly associated with adequacy (P = .02). Standardized collection did not improve overall cell block cellularity.'] Is adequacy assessment of endoscopic ultrasound-guided , fine-needle aspirations of pancreatic masses for theranostic studies : optimization of current practices warranted?