Flow cytometric immunophenotyping including Bcl-2 detection on fine needle aspirates in the diagnosis of reactive lymphadenopathy and non-Hodgkin's lymphoma.

Background: Fine-needle aspiration (FNA) with immunophenotyping by immunocytochemistry (IC) on cytospins has recently received increased consideration in the diagnosis of lymphoma. The aim of our study was to establish the diagnostic value of a four-color flow cytometric (FCM) panel, including cytoplasmic Bcl-2, in cytologic diagnosis of malignant non-Hodgkin's lymphoma (NHL) and reactive lymphoid hyperplasia (RH).

Methods: We investigated 424 FNAs from 396 patients. FCM panel included lambda/kappa/CD19/CD5, CD23/CD10/CD20/CD19, CD4/CD7/CD8/CD3 and Bcl-2/CD10/CD19/CD3 in fluorescein isothiocyanate, phycoerythrin, and peridinin chlorophyll protein or a tandem conjugate of R-phycoerythrin and indodicarbocyanine and allophycocyanin. Bcl-2 expression was evaluated separately for gated B and T cells.

Results: In 97% of 172 RH samples, FCM was concordant with the diagnosis. FCM gave correct immunologic diagnosis in 95% of low-grade B-cell NHLs, 78% of high-grade B-cell NHLs, and 53% of T-cell lymphomas. Malignant B cells had higher Bcl-2 expression than did reactive B and T cells. This helped to establish a correct diagnosis especially in cases where no clear-cut monoclonality could be shown by kappa/lambda staining or where there was no expression of surface light chain. The highest Bcl-2 expression was found in follicular lymphomas.

Conclusion: Our FCM panel allowed precise classification of NHL in FNA material in 89.5% of all samples. Bcl-2 staining can be recommended for primary differentiation between reactive hyperplasia and NHL.