CD48 expression in T-lymphoblastic leukemia/lymphoma and mature T-cell neoplasms: role in detecting measurable residual disease and potential confounders, a single-institution retrospective review

Objectives Assessing the stage of maturation is critical for the classification of T-cell neoplasms and is helpful in minimal/measurable residual disease (MRD) testing for T-lymphoblastic leukemia (T-ALL). This study analyzes the utility of CD48 in characterizing T-cell neoplasms at diagnosis and posttherapy. Methods This retrospective review characterizes the expression of CD48 in T-ALL and mature T-cell neoplasms at diagnosis and posttreatment. CD48 intensity was assessed qualitatively by flow cytometry relative to the background T cells. Potential confounders were also evaluated. Results T cells show increases in CD48 expression with progressive maturation, with high-level expression on mature T cells. CD48 expression by flow cytometry was decreased to absent (compared with expression on mature T cells) in 100% of T-ALL cases at diagnosis and in 92% of cases positive for MRD posttherapy. By contrast, among mature T-cell neoplasms, CD48 expression at diagnosis overlapped with expression on background mature T cells in most cases (91%). Reduced CD48 expression on background, nonneoplastic T cells was seen in the setting of alemtuzumab therapy and in samples with glycosylphosphatidylinositol (GPI)–deficient populations. Conclusions CD48 expression is diminished compared with normal background T cells in most cases of T-ALL at diagnosis and posttherapy, whereas it was typically retained in mature T-cell/natural killer–cell neoplasms. While CD48 levels may fluctuate after chemotherapy in T-ALL, reduced CD48 can be used as a marker of immaturity in most MRD cases. Potential confounders in the assessment of CD48 include alemtuzumab therapy and the presence of GPI-deficient populations.