Utility of Flow Cytometry Immunophenotyping in Fine-needle Aspirate Cytologic Diagnosis of Non-Hodgkin Lymphoma: A Series of 252 Cases and Review of the Literature

Flow cytometry (FC) immunophenotyping of fine-needle aspiration (FNA) has been reported to be useful in the diagnosis of non-Hodgkin lymphomas (NHL). The authors reviewed their 5-year experience to assess the ability that FC has in improving the diagnostic capacity of cytomorphology in the diagnosis and subclassification of NHL according to the World Health Organization's classification. FC was performed on 252 FNA specimens. These included 123 cases of NHL (89 primary and 34 recurrent lymphomas). The FC immunophenotyping included CD3, CD4, CD8, CD10, CD19, CD20, CD45, and [kappa]/[lambda] antibodies combinations in the screening panel and additional panels for B or T lineage in the presence of positivity for lymphoma after the screening. An immunologic diagnosis was obtained by FC in 90% (111/123) of cases identified as NHL. FC was able to improve the total number of NHL detected in 8 cases where cytomorphology had failed to do so. In 7% (9/123) of cases, FC failed to formulate a diagnostic hypothesis owing to the sample inadequacy; 2 cases (2%) were not identified as lymphomas by FC (1 of them considered only "suggestive" also by cytomorphology); 1 case was not identified neither by FC, nor by cytomorphology. In cases having a histologic follow-up, levels of diagnostic sensitivity and specificity of the combination cytomorphology/FC were 97% and 94%, respectively. FC applied to FNA enhanced the diagnostic potential of cytologic diagnosis and subclassification of NHL, thus avoiding the need for invasive surgical biopsies in many cases.