Factors determining whether diffuse large B‐cell lymphoma samples are detected by flow cytometry

Abstract

AbstractIntroductionFlow cytometry (FCM) is widely used in the diagnosis of mature B‐cell neoplasms (MBN), and FCM data are usually consistent with morphological findings. However, diffuse large B‐cell lymphoma (DLBCL), a common MBN, is sometimes not detected by FCM. This study aimed to explore factors that increase the likelihood of failure to detect DLBCL by FCM.MethodsCases with a final diagnosis of DLBCL that were analysed by eight‐colour FCM were retrospectively collated. Clinical, FCM, histopathological and genetic data were compared between cases detected and cases not detected by FCM.ResultsDLBCL cases from 135 different patients were analysed, of which 22 (16%) were not detected by FCM. In samples not detected by flow cytometry, lymphocytes were a lower percentage of total events (p = 0.02), and T cells were a higher percentage of total lymphocytes (p = 0.01). Cases with high MYC protein expression on immunohistochemistry were less likely to be missed by FCM (p = 0.011). Detection of DLBCL was not different between germinal centre B‐cell (GCB) and non‐GCB subtypes, not significantly affected by the presence of necrosis or fibrosis, and not significantly different between biopsy specimens compared to fine‐needle aspirates, or between samples from nodal compared to extranodal tissue.ConclusionThe study identifies several factors which affect the likelihood of DLBCL being missed by FCM. Even with eight‐colour analysis, FCM fails to detect numerous cases of DLBCL.