Post written by Jae Hee Cho, MD, PhD, and Sung Ill Jang, MD, PhD, from the Division of Gastroenterology, Department of Internal Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, and See Young Lee, MD, from the Division of Gastroenterology, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.

EUS-guided fine-needle biopsy (FNB) is the standard for diagnosing solid pancreatic masses, but tissue adequacy can still be limited with small or technically demanding lesions. Liquid-based cytology (LBC) prepared from the residual fluid of FNB specimens offers a complementary diagnostic source that is often overlooked. In this prospective, randomized, crossover trial, we directly compared 2 widely available LBC platforms—precipitation-based SurePath (BD, Franklin Lakes, NJ, USA) and filtration-based ThinPrep (Hologic BV, Zaventem, Belgium)—using paired specimens from 102 patients with suspected pancreatic malignancy.

Most previous LBC studies in pancreatic cytology have compared LBC against conventional smears rather than comparing LBC techniques against each other. Platform choice has therefore been driven largely by institutional availability, despite meaningful mechanistic differences—density gradient centrifugation versus filter-based collection—that could affect cellularity, slide quality, and ultimately diagnostic performance. To our knowledge, this is the first prospective randomized trial directly comparing precipitation- and filtration-based LBC in EUS-guided FNB residual fluid from pancreatic masses.

SurePath achieved significantly higher diagnostic accuracy (97.0% vs 83.9%; P = .002) and sensitivity (97.0% vs 83.7%; P = .002) than ThinPrep, with comparable specificity and positive predictive value. SurePath slides showed markedly better even cell distribution (99.0% vs 7.8%; P < .001), higher cellularity, more frequent 3-dimensional clusters, and clearer preservation of malignant features (hyperchromasia, coarse chromatin, and conspicuous nucleoli). Mean interpretation time was nearly halved (2.8 vs 4.6 minutes). Multivariate analysis confirmed cellularity, even distribution, and 3-dimensional clusters as the dominant determinants of diagnostic success.

These findings indicate that LBC platform choice is not technically neutral; precipitation-based preparation appears better matched to the cellular characteristics of FNB residual fluid. Future work should validate these results across centers and explicitly assess whether SurePath samples preserve sufficient material for downstream molecular ancillary testing such as KRAS analysis or next-generation sequencing.

Cytology from FNB residual fluid is often discarded, yet our data show it can be diagnostically decisive—particularly when histologic cores are inadequate or atypical. Incorporating SurePath LBC into routine EUS-guided FNB workflows requires no procedural change, adds minimal cost, and may meaningfully improve diagnostic yield even in settings without rapid on-site cytologic evaluation infrastructure.

Representative cases diagnosed as malignant by liquid-based cytology (LBC) but not by fine-needle biopsy (FNB). A–C, Case 1: Malignancy diagnosed on LBC but deemed inadequate on FNB. A, ThinPrep slide (×630) showing anisocytosis, nuclear pleomorphism, and conspicuous nucleoli, interpreted as suspicious for malignancy; B, SurePath slide (×630) showing anisocytosis, nuclear pleomorphism, hyperchromasia, coarse chromatin, and conspicuous nucleoli, confirming a cytologic diagnosis suspicious for malignancy; C, FNB slide (×630) showing no tissue component, interpreted as inadequate. D–F, Case 2: Malignancy diagnosed on precipitation-based LBC (SurePath) but classified as atypical on FNB. D, ThinPrep slide (×630) showing anisocytosis without other malignant features, interpreted as atypical, E, SurePath slide (×630) showing anisocytosis, nuclear pleomorphism, and coarse chromatin, interpreted as suspicious for malignancy, F, FNB slide (×630) showing a small cluster of dysplastic cells, but the degree of atypia does not meet the criteria for malignancy, interpreted as atypical.

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