Immunophenotypic features of constant beta chain–restricted Sézary cells showing complex multicluster composition and overlap with benign T-cell subsets. (A) Density plots showing extensive immunophenotypic overlap between constant beta chain–restricted Sézary cells from patients with CTCL (red lines), and benign CD4⁺ T cells from patients with inflammatory dermatoses (blue lines). Double lines depict 2 standard deviations. (B) Metaclustering (K-means) of constant beta chain–restricted Sézary cell clusters showing distinct immunophenotypic subtypes on 2-dimensional projections (described as class 1-6). (C) Circos plot depicting the incidence (segments) and observed combinations (ribbons) of Sézary cell metaclusters. (D) Contribution of each immunophenotypic class of Sézary cell to the total Sézary cell count based on absolute numbers of cells per microliter (left) and percentage of total Sézary cells (right). Box and whiskers: median, interquartile range and total range. Asterisks (∗), (∗∗), and (∗∗∗) indicate P < .05, P < .01, and P < .0001, respectively, compared to class 1. (E) Incidence of each immunophenotypic class of Sézary cell (first positive sample only) in patients with mycosis fungoides (grey bars) and Sézary syndrome (black bars). Asterisk (∗) indicates P < .05. (F) Examples of patients with Sézary syndrome (top) and mycosis fungoides (bottom), showing variability of Sézary cell metacluster composition and abundance on serial samples.