Sézary cells show heterogeneous phenotypes reflecting inter- and intrapatient diversity. (A) An automatic population separator (APS) plot based on all parameters included in the T-CLPD antibody panel showed the normal distribution of CD4⁺ T cells derived from 10 age- and sex-matched HCs (reference database). The green inner and outer lines represent, respectively, the first and second standard deviation of normal CD4⁺ T cells (green dots) and their corresponding population medians (larger green dots). (B) Phenotypically altered CD4⁺ T cells (red dots) from 24 patients with SS are depicted against the reference database and illustrate their heterogeneous and aberrant expression patterns compared with normal CD4⁺ T cells. Examples of 2 SS samples showing a tumor population with 1 homogeneous (C) or 2 immunophenotypically distinct (D) aberrancies.