Incremental Diagnostic Yield of On-site Quick-prep Smear versus Cell-block Cytology in EUS-FNA of Solid and Cystic Masses

Abstract

Purpose: In many centers that perform a high volume of endoscopic ultrasound-fine needle aspiration (EUS-FNA), cytology from both on-site quick prep smears (QPS) and from a centrifuged cell-block (CB) are evaluated. The additive value of performing both instead of one of these tests, however, has not been well studied. The aim of this study is to evaluate the independent diagnostic performance of QPS and CB in specimens obtained from EUS-FNA, and to assess the incremental yield of each test. Methods: A retrospective review was conducted of all EUS-FNA procedures performed at a tertiary referral hospital between August 2006 and July 2008. Procedures in which either QPS or CB was not performed were excluded. All FNAs were performed using a 22 gauge needle (Cook Medical, Bloomington IN). Mass location and size, number of needle passes, cytology adequacy and diagnosis from both QPS and CB were recorded. Diagnoses were categorized as non-neoplastic, atypical, and neoplastic. Data were analyzed with Student's t-test and Chi-Square test where appropriate. Results: Specimens from 442 EUS-FNA procedures met the inclusion criteria and were evaluated. 306 masses were solid (70% pancreatic, 30% other) and 136 were pancreatic cysts. The mean patient age was 65 and the mean mass size was 2.8 cm. The overall diagnostic yield of EUS-FNA (i.e., percentage of procedures in which cytology was adequate to make a diagnosis) was 76.5%, but differed significantly between solid and cystic masses (88.2% vs. 50%, P < 0.0001). When examined independently, the diagnostic yield of QPS did not differ from CB (72.6% vs. 70.1%). For all masses diagnosed as neoplastic based on EUS-FNA, the sensitivity of QPS was significantly greater than CB (97.3% vs. 92.4% P<0.05). In 59 (13.4%) of the 442 cases, the diagnosis between QPS and CB was discordant. In this group, QPS was more likely to make an additional diagnosis (36 cases, incremental yield 8.1%) than CB (23 cases, incremental yield 5.2%; P<0.05). This difference was seen only in solid but not cystic masses. Conclusion: On-site quick prep smears (QPS) from EUS-FNA specimens are more sensitive for diagnosing neoplasia than cell block (CB) and provide a higher incremental diagnostic yield, highlighting the importance of this practice. Prospective studies evaluating the incremental cost effectiveness of processing the CB in the setting of a diagnostic QPS should be considered.