Is mediastinal fine needle aspiration cytology required or redundant? A single institution-based correlation study with core needle biopsy.

Introduction: Fine Needle Aspiration cytology (FNAC) and core needle biopsy (CNB) are rapid, minimally invasive and useful techniques to evaluate mediastinal lesions.

Objectives: To compare cytopathology with histopathology of mediastinal lesions and analyse reasons for discordance.

Material & Methods: Retrospective analysis was done in a tertiary care centre in North West India over a period of seven and half years from 1July 2016 to 31st December 2023. Only those patients who had undergone FNAC and trucut biopsy of mediastinal masses were included. The cytopathology and histopathology slides were studied to analyse causes of discordance. Sensitivity, specificity, positive and negative predictive values of FNAC were calculated keeping histopathology as gold standard.

Results: Out of 57 cases analysed, eight cases were non diagnostic on cytology. Cytology could effectively classify a lesion as non neoplastic (7) or neoplastic (42). For further subtyping, histopathology and Immunohistochemistry (IHC) were required. Out of 27 cases of cytological - histopathological discordance, 8 cases had sampling error, 15 cases had limited concordance where FNAC could predict possibility of tumor and 4 cases were discordant where subtyping of malignancy varied on CNB. Sensitivity of FNAC to predict definite diagnosis was 90.2 %, specificity was 50 %, positive predictive value of FNAC to give a definite diagnosis was 93.9 %, negative predictive value was 37.5 %.

Conclusion: Evaluation of mediastinal masses requires combination of cytology, histopathology and ancillary techniques like IHC. FNAC and CNB are complementary modalities and both are essential for rapid, accurate and comprehensive diagnosis.