Splenic Lymphoid Subsets With Less Well-Recognized Phenotypes Mimic Aberrant Antigen Expression

Abstract

OBJECTIVES: Flow cytometry can assist in the diagnosis of lymphoma by identifying aberrant antigen expression. Recognition of aberrancy requires knowledge of the phenotype of normal lymphoid cells. METHODS: Lymphoid subsets were characterized in 20 spleens removed for traumatic rupture, using 8-color flow cytometry. RESULTS: Normal variation in splenic lymphoid subsets was highlighted and several well-recognized subsets were identified: CD5+ B cells (20/20 specimens), CD7- T cells (20/20), and CD3 brightγδT cells (16/20). In addition, less well-recognized lymphoid subsets that resemble those described in lymphoma were identified in all specimens: CD5- T cells (4.5 ± 5.1% of T cells), CD2- natural killer (NK) cells (38 ± 7% of NK cells), and CD7dim+ NK cells. Similar populations were identified in 20 control peripheral blood specimens, where they represented a smaller proportion of total lymphoid cells. CONCLUSIONS: Familiarity with the phenotype of normal lymphoid subsets can help prevent misinterpreting flow cytometric data. Furthermore, in the context of neoplastic cells, the phenotype may suggest expanded normal subsets rather than aberrant antigen expression.