The Power of Flow Cytometry in the Cytopathologic Diagnosis of Lymphoid Lesions.

[BACKGROUND] Cytological examination of a fine-needle aspirate (FNA) is a minimally invasive modality that is increasingly used in the diagnosis of lymphoma. Flow cytometry and other ancillary tests make an important contribution to the diagnostic value of FNAs of lymphoid lesions. This review follows the recent publication of the first edition of the WHO Reporting System for Lymph Node, Spleen, and Thymus Cytopathology. This WHO volume provides a framework for assessment of cytopathological samples and presents in detail the contribution of ancillary studies, including flow cytometry.

[SUMMARY] The current review is designed to complement the WHO volume. It presents criteria for adequacy of FNA specimens assessed by flow cytometry and includes strategies to determine the degree of blood contamination of FNA samples. Evidence for the contribution of flow cytometry to the diagnostic value of FNA is reviewed. The role of TRBC1 and TRBC2 in the assessment of T-cell populations is presented. Strengths of flow cytometry, along with its limitations, are presented.

[KEY MESSAGES] Provided these limitations are properly understood, the inclusion of flow cytometry as an ancillary modality makes a substantial contribution to FNA assessment.