Figure 1.

Clinical criteria for staging of mycosis fungoides (MF) and Sézary syndrome (SS). SS is classified as stage IVA₁ disease and is distinguished from MF by a high blood tumor burden. Diagnostic “B2” blood criteria required for SS include Sézary cells ≥ 1000 cells/μL, CD4/CD8 ≥ 10, CD4⁺CD7⁻ cells > 30% or CD4⁺CD7⁻ cells ≥ 40%, with an identical T-cell clone detected in blood and skin. Stage IIIB requires B1 blood involvement not meeting the B2 threshold for SS. The most distinguishing qualifier for each stage is noted. The table is adapted from the ISCL/European Organization for Research and Treatment of Cancer (EORTC) classification criteria in Olsen et al. [33]. BSA, body surface area affected. Erythroderma, BSA > 80%.