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).

Figure 1

Flow diagram for 296 patients referred for EUS-FNA. EUS-FNA: EUS-guided fine-needle aspiration.

Figure 2

Imaging manifestations and pathologic manifestations of IgG4-related diseases. A, MRCP: the lumen of the pancreatic segment of the common bile duct appears narrowed, forming a thin line. This is accompanied by dilatation of the bile ducts both above and below it, including the intrahepatic and extrahepatic bile ducts. The widest part of the common bile duct measures approximately 1.7 cm. B, EUS: in the head of the pancreas, there is a hypoechoic area with irregular but well-defined borders. Its cross-sectional size measures approximately 3.98 × 1.96 cm. This area exhibits medium elasticity and a characteristic imaging texture. C, CT: the pancreas displays diffuse swelling, along with thickening of the walls in the middle and upper bile ducts. D, PET/CT: the bile duct wall shows increased FDG uptake with an SUV_max of 2.4. Nodular increased FDG uptake is particularly noticeable in the neck and body of the pancreas on conventional scans, with an SUV_max of 5.0. FDG uptake remains persistently increased on delayed scans, reaching an SUV_max of 6.0. E, Pancreatic EUS-FNA puncture (HE stain): the findings indicate diffuse chronic inflammatory cell infiltration, along with the proliferation of interstitial fibrous tissue and sclerosis. Pancreatic ductal hyperplasia is also observed. F, Pancreatic EUS-FNA puncture (CD138): scattered positive results are observed. G and H, Pancreatic EUS-FNA puncture (IgG and IgG4): in some areas, the IgG4/IgG ratio exceeds 40%, and the IgG4 count is greater than 10 HPF. CT: computed tomography; FDG: fluorodeoxyglucose; HE: hematoxylin and eosin; HPF: high-power field; MRCP: magnetic resonance cholangiopancreatography; PET/CT: positron emission tomography/computed tomography; SUV_max: standardized uptake value.