Diagnostic accuracy and safety of endoscopic ultrasound-guided fine needle biopsy for evaluating mediastinal pathologies

BACKGROUND The mediastinum comprises vital anatomical structures and can be affected by diverse benign and malignant pathologies. Imaging modalities such as computed tomography, magnetic resonance imaging, and positron emission tomography assist in initial evaluation, but histopathological confirmation remains the diagnostic gold standard. Endoscopic ultrasound (EUS) enables real-time, minimally invasive sampling of mediastinal lesions. EUS-guided fine needle biopsy (FNB) demonstrated high diagnostic accuracy with a favourable safety profile. Despite its established utility in high-income settings, data on the role of EUS in evaluating mediastinal pathologies in low- and middle-income countries, such as Pakistan, remain limited. AIM To assess the diagnostic yield of EUS-guided FNB in evaluating mediastinal pathologies and its role in guiding management in low- and middle-income countries. METHODS This single-centre retrospective study was conducted at Aga Khan University Hospital, Karachi, from June 2020 to June 2024, involving adults (≥ 18 years) who underwent EUS-guided FNB for mediastinal pathology. Franseen needles with capillary suction were used without rapid on-site evaluation, yielding adequate histopathological samples in all cases. Data included demographics, radiological, procedural, and histopathological details, treatment, and outcomes. Statistical analysis was performed using Statistical Package for the Social Sciences version 23, with receiver operating characteristic curve analysis used to assess the diagnostic performance of EUS-guided FNB. RESULTS A total of 77 patients (mean age: 54.4 ± 14.1 years; 55.8% male) underwent EUS-guided FNB for mediastinal pathology. Most (81.8%) were symptomatic, with lymphadenopathy or masses mostly detected on computed tomography (79.2%). Adequate tissue diagnosis was achieved in 94.8%; 41.6% were malignant. EUS-FNB showed 88.9% (95% confidence interval: 74.7-95.6) sensitivity, 100% (95% confidence interval: 91.4-100) specificity, and an area under the curve of 0.94. Malignant cases had significantly larger lymph nodes (2.3 ± 0.9 cm vs 1.57 ± 0.6 cm, P = 0.009) and masses (median 7.8 cm vs 4.2 cm, P = 0.001). Most EUS procedures (96.1%) were performed using a 22G needle. The mean number of needle passes was 2.1 ± 0.8. No post-procedure complications occurred. Common diagnoses included reactive lymphoid tissue (20.8%), tuberculosis (14.3%), and lymphoma (11.7%). Conservative therapy was the most common treatment (28.6%). Overall, 68.8% survived and 13.0% died. CONCLUSION EUS-guided FNB is a highly accurate and safe modality for diagnosing mediastinal pathologies, offering excellent diagnostic yield without procedure-related complications and effectively guiding management of both benign and malignant cases.