Comparison of Routine Brush Cytology and Fluorescence in Situ Hybridization (FISH) for Assessment of Biliary Strictures: A Single Teaching Institution Experience

Document Type

Conference Proceeding

Publication Date

3-1-2024

Publication Title

Lab Invest

Abstract

Background: Biliary brushing cytology is the standard of care for the assessment of biliary strictures, but it suffers from low sensitivity and high rate of atypical diagnoses, especially in the setting of stents. More recently, FISH has become an increasingly valuable adjunct. The aim of this study is to evaluate the diagnostic performance of FISH in our institution and compare the results with routine cytology. Design: We conducted a retrospective study and selected biliary brushing cases with available FISH results from April 2019 to March 2023. We retrieved surgical pathology biopsy and resection (SP) diagnoses and at least 6-month clinical follow up data on available cases. FISH was performed with the UroVysion test (Abbott Molecular, Inc.), which includes centromere probes for chromosomes 3, 7, 17 and a locus specific probe for 9p21 (CDKN2A). A case was considered FISH positive (P) if five or more cells exhibited polysomy on two or more of the four probes or homozygous deletion of the 9p21 CDKN2A gene. A case was considered FISH equivocal (E) if trisomy 7 or heterozygous deletion of 9p21 CDKN2A was observed. The sensitivity and specificity were calculated. SP diagnoses were used as gold standards for "true positive", while "true negative" was based on at least 6-month negative clinical follow up data including negative cytology and negative SP. Results: A total of 228 cases were retrieved; age range 37-89. For cytology results: 151 negative (N) (125 with negative follow up, 26 SP positive); 55 atypical (A) (40 with negative follow up, 15 SP positive); 6 suspicious (S) (all SP positive), and 16 positive (P) (all SP positive). For FISH results: 105 negative (96 with negative follow up, 9 SP positive); 71 equivocal (65 negative follow up, 6 SP positive), 52 positive (4 negative follow up, 48 SP positive). When calculating performance measures, cytology atypical and FISH equivocal were excluded; cytology suspicious was considered positive. The sensitivity and specificity of cytology were 45.8% and 100%. The sensitivity and specificity of FISH were 84.2% and 96.0%. Conclusions: We report a large cohort for comparison of FISH and cytology in detecting malignant biliary strictures. FISH was more sensitive than cytology (84.2% vs 45.8%). FISH rarely produces false positive results (specificity 96.0% vs 100%). Routine cytology had no false positive results and is the gold standard for clinical management. Equivocal FISH results have low positive predictive value, nearly equal to a negative FISH result.

Volume

104

Issue

3

First Page

S427

Last Page

S428

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