Utility of Flow Cytometry in the Diagnostic Evaluation of Recurrent or Persistent Nodular Lymphocyte-Predominant Hodgkin Lymphoma

Abstract

Abstract Objectives We previously reported that lymph nodes involved by nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) had unique flow cytometric features. To further validate their diagnostic utility, we have examined the flow cytometry features in cases of persistent lymphadenopathy (LAD) prior to the diagnosis of NLPHL or recurrent LAD following diagnosis and treatment for NLPHL. Methods We retrospectively identified nine patients (2-3 specimens per patient for a total of 20 specimens) with persistent or recurrent lymphadenopathy before or after they were diagnosed with NLPHL between the ages of 13 and 76 years. Their histopathology diagnoses were reviewed and flow cytometry data were reanalyzed. Results Based on our published criteria (Am J Clin Pathol 2016;145:107-115), positive flow cytometry findings (at least 12% of T cells expressing CD57 or at least 3% of T cells coexpressing CD4 and CD8) were seen in 18 specimens. Based on histopathology, 11 of them were correctly diagnosed as NLPHL, 3 of them initially underdiagnosed as atypical lymphoid proliferation, and 4 of them initially incorrectly diagnosed as negative or progressive transformation of germinal centers (PTGCs). The flow cytometry studies showed similar expression patterns of CD57, CD4, and CD8 in T cells and very similar high percentages of CD57+ T cells and CD4+CD8+ T cells between initial biopsies and subsequent biopsies in these patients. Negative flow cytometry findings were seen in two specimens pathologically confirmed as negative for NLPHL in two patients after treatment. Their initial diagnostic specimens showed positive flow cytometry findings, different from that seen in the subsequent specimens posttreatment. Conclusion Flow cytometry appears to be a useful adjunct in detecting early or relapsed NLPHL, especially in atypical lesions. The presence of positive flow cytometry features is very sensitive in detecting recurrent or persistent NLPHL, while absence of positive flow cytometry features helps rule out NLPHL.