Diagnostic efficacy of cytologic smear and pathologic histology in the differential diagnosis of distal biliary stricture via EUS-guided fine-needle aspiration

Abstract

Background and objectives: Distal biliary strictures (DBSs) can be caused by various malignancies, making accurate and early diagnosis crucial. Histopathology is the gold standard for diagnosis, with several methods available for tissue sampling. This study evaluates the performance of EUS-guided fine-needle aspiration (EUS-FNA) cytologic smears and histopathology in diagnosing suspected malignant DBSs.

Methods: A retrospective cohort study was conducted on patients who underwent EUS-FNA between January 2017 and January 2023 for DBSs. Demographic, imaging, procedural, and clinical data were collected. The diagnostic performance of EUS-FNA cytology, histology, and their combination was assessed in terms of sensitivity, specificity, positive predictive value, and negative predictive value. Subgroup analyses were conducted based on imaging and endoscopy characteristics.

Results: EUS-FNA for cytology had a sensitivity of 69.1% and specificity of 97.5%. EUS-FNA histology had a sensitivity of 76.4% and specificity of 99.1%. There was no difference in diagnostic efficacy between the two above (P > 0.05). Combining cytology and histology improved sensitivity to 82%. When 20 cases (6.8%) with histological slide failures were considered as negative, histologic sensitivity was 69.1%, completely consistent with cytology alone (P = 1). The presence of a mass shadow on computed tomography or magnetic resonance imaging was associated with higher cytologic diagnostic sensitivity compared with simple stenosis without a mass shadow (57.4% vs. 75.9%, P = 0.011). The larger the mass, the higher the cytologic diagnostic sensitivity. The radiologist's diagnostic imaging tendencies, that is, malignant, benign, and indeterminate, also affected cytologic diagnostic sensitivity (78.2% vs. 63.9% vs. 51.9%, P = 0.002). Furthermore, among our cohort of 118 patients diagnosed with benign DBSs, a notable subset of 33 individuals (28%) received a diagnosis of IgG4-related disease.

Conclusion: EUS-FNA histology combined with cytology was a reliable diagnostic method. There is no difference in diagnostic efficacy between EUS-FNA cytology and histology, irrespective of considering instances of histological slide failure. The presence of a mass shadow on computed tomography or magnetic resonance imaging and the size of the mass influenced the diagnostic efficacy of cytology. Additionally, IgG4-related diseases, accounting for a significant proportion of cases, were important in the differential diagnosis of these strictures.

Keywords: Differential diagnosis; Distal biliary stricture (DBS); EUS-guided fine-needle aspiration (EUS-FNA); Histopathology; IgG4-related disease (IgG4-RD).