CD4+CD26- lymphocytes are useful to assess blood involvement and define B ratings in cutaneous T cell lymphoma.

Bernengo et al. reported that >30% CD4+CD26- lymphocytes detect blood involvement in patients with mycosis fungoides (MF) and Sézary syndrome. In addition, the ISCL/EORTC suggested that this threshold might serve as a criterion for the B2 blood rating for staging. In this manuscript, we report our experience with measurement of CD4+CD26- and CD4+CD7- cells, Sézary cell counts, and aberrant T cells with diminished expression of CD2, CD3, or CD5 antigens. CD4+CD26- ≥30% occurred in 15 of 373 (4.0%) patients with MF, 33 of 47 (70%) patients with erythrodermic cutaneous T cell lymphoma (ECTCL) and 2 of 54 (4%) patients with inflammatory skin diseases. CD4+CD26- measurements provided a more reliable assessment of neoplastic cell numbers in the blood than Sézary cell or CD4+CD7- percentages. CD4+CD26- measurements may be used to define B ratings for staging with B2 defined as CD4+CD26- ≥ 1000/μL, plus clonality or phenotypically abnormal cells.