EUS FNAC without rapid on-site evaluation is comparable to EUS FNB with macroscopic on-site evaluation in evaluation of intra-abdominal masses.

Introduction: Endoscopic ultrasound-guided tissue acquisition (EUS TA) has become the mainstay for tissue diagnosis of abdominal mass lesions. Two widely used and accepted methods for obtaining diagnostic material, namely fine needle aspiration cytology (EUS FNAC) and needle core biopsy (EUS FNB), have distinct advantages and disadvantages. We compared the diagnostic accuracy of EUS FNAC without on-site pathology and EUS FNB taken within the same endoscopic session in evaluation of intra-abdominal masses.

Methods: In this prospective observational study, we included patients undergoing EUS FNAC and EUS FNB for the diagnosis of solid intra-abdominal masses. Sample size was calculated based on the available literature. Location, origin, dimensions of the intra-abdominal masses and number of passes taken were recorded. EUS-guided FNAC followed by EUS-guided FNB was done back-to-back during the same endoscopic session. FNAC smears were prepared and air dried and alcohol-fixed slides were prepared. Adequacy of the FNB specimen was judged visually. The diagnostic accuracy of FNA and FNB specimens was then calculated based on the final diagnosis and compared.

Results: Of the 58 patients included, 50% of patients were females with a mean age of 53.91 ± 17.16 years. Nineteen pancreatic masses (32.7%), three gastric mass lesions (5.1%), one adrenal mass (1.7%), one liver mass (1.7%), three gallbladder masses (5.1%) and 31 lymph nodal masses (53.4%) were sampled. With EUS FNB, malignancy was diagnosed in 38/58 (65.5%), benign diseases in 19/58 (32.7%) and 1/58 (1.7%) was inconclusive. Number of passes was more in the EUS FNAC group compared to EUS FNB, but not statistically significant. Sensitivity and specificity of EUS FNAC without rapid on-site evaluation (ROSE) were found to be 92.4% and 100%, respectively. Diagnostic accuracy of EUS FNAC was 93.1% and when compared with EUS FNB with macroscopic on-site evaluation (MOSE), no statistically significant difference was noted.

Conclusion: EUS FNAC and EUS FNB are comparable for the diagnosis of intra-abdominal masses in terms of diagnostic accuracy, sample adequacy, number of passes and safety. In resource-constraint settings, either EUS FNAC or EUS FNB alone may be sufficient for diagnosis with EUS FNB being preferred in select cases where maintained tissue architecture is needed.