Flow cytometry immunophenotyping of fine-needle aspiration specimens: utility in the diagnosis and classification of non-Hodgkin lymphomas.

AIMS:To establish the utility of flow cytometry (FCM) for screening and diagnosis of B cell non-Hodgkin lymphoma (B-NHL) from lymphoid tissue samples obtained by fine-needle aspiration (FNA). METHODS AND RESULTS:We compared prospectively FCM versus cytology/histology analysis of FNA samples for the diagnostic screening and further World Health Organization (WHO) subclassification of B-NHL. FCM and cytology showed a high degree of agreement (93%); however, diagnosis of reactive processes (RP), B-NHL and T-NHL by FCM showed higher sensitivity than cytology (92-100% versus 64-94%, respectively), without false positive NHL cases. The antibody combination used did not allow a positive diagnosis of Hodgkin lymphoma as distinct from a RP. A high concordance rate was found between FCM and histopathology (74%) in subtyping B-NHL. In this regard, mantle-cell lymphoma and chronic lymphocytic leukaemia/small lymphocytic lymphoma showed the highest degree of agreement (100% concordant rates). In turn, FCM showed higher sensitivity/specificity in classifying follicular lymphoma (FL) and large B cell lymphomas, while the opposite occurred for marginal-zone and lymphoplasmacytic lymphomas. CONCLUSIONS:FCM enhances the diagnostic ability of FNA cytology, playing a crucial role in a rapid and accurate differential diagnosis between RP, B-NHL and T-NHL. In addition, immunophenotyping of FNA samples contributes to a more precise subclassification of B-NHL when combined with histopathology and genetic/molecular data.