Flow cytometric analysis of aberrant CD7 expression within the stem cell subset. The CD34⁺CD38^– stem cells were identified within the CD45^lowSSC^lowCD14^– cells (left panel), and the presence (A) or absence (B) of aberrant CD7⁺ cells were evaluated by using a bivariate plot of SSC-A vs CD7 (middle panel). The right panel displays backgating of CD7⁺ stem cells (black dots) into the CD45^lowSSC^lowCD14^–CD34⁺CD38^- population (gray). (C) Absolute number of CD34⁺CD38^– CD7⁺ cells according to case-control status. The dashed line denotes number of CD34⁺CD38^– CD7⁺ cells required for aberrant CD7 expression. Five cells or more were regarded as a positive lower limit. Patients with <5 CD34⁺CD38^– CD7⁺ cells are not shown as dots in the figure (case subjects, n = 20; control subjects, n = 33). The Pearson χ² test was used to calculate P values, with the positive lower limit of 5 cells being the cutoff for yes/no for aberrant CD7 expression.