Fine-Needle Aspiration Diagnosis of Lymphoma Based on Cytomorphology Alone: How Accurate is it? - A Cyto-Histopathology Correlative Study

CONTEXT: Fine-needle aspiration cytology (FNAC) is a rapid and accurate first-line diagnostic modality in lymphadenopathy. AIMS: To determine the utility of FNAC for the diagnosis of lymphoma and highlight the various pitfalls in morphological interpretation. SETTINGS AND DESIGN: This was a retrospective study of 3 years duration in which cytology diagnosis was compared with the follow-up histopathology diagnosis wherever available. RESULTS: A cytodiagnosis of lymphoma was made in a total of 868 cases (2.8%) out of nearly 33,000 FNAC performed during the study period; 556 (64.1%) cases were diagnosed as non-Hodgkin lymphoma (NHL), 198 (22.8%) as Hodgkin lymphoma (HL), and in 114 (13.1%) cases, a cytological diagnosis of lymphoma without further categorization was given. Histopathological reports were available in 348 cases, with an overall concordance rate of 93.1% (324), which was slightly higher in the HL cases (95.8%) as compared to NHL (91.7%). Twenty-four cases (6.9%) showed discordant cytological diagnosis with subsequent histopathology. The main reasons for the erroneous diagnosis were the over-interpretation of the germinal center cells as atypical lymphoid cells, over-interpretation of immunoblasts with prominent nucleoli as Hodgkin cells, and sheets of monomorphic lymphoid cells interpreted as low-grade lymphoma. CONCLUSION: Cytomorphology alone can make a correct basic diagnosis of lymphoma with a high degree of accuracy. The errors in interpretation can be further reduced by careful attention to the diagnostic pitfalls and common differential diagnoses.