Two conferences were sponsored by the International Society for Cutaneous Lymphomas (ISCL) to gain consensus on definitions and terminology for clinical use in erythrodermic cutaneous T-cell lymphoma (E-CTCL). Three subsets of E-CTCL were defined: Sézary syndrome ("leukemic phase" E-CTCL), erythrodermic mycosis fungoides (secondary E-CTCL that develops in patients with mycosis fungoides), and E-CTCL, not otherwise defined. The hematologic criteria recommended for Sézary syndrome are intended to identify patients with a worse prognosis compared with the other E-CTCL subsets and consist of one or more of the following: (1) an absolute Sézary cell count of 1000 cells/mm3 or more; (2) a CD4/CD8 ratio of 10 or higher caused by an increase in circulating T cells and/or an aberrant loss or expression of pan-T cell markers by flow cytometry; (3) increased lymphocyte counts with evidence of a T-cell clone in the blood by the Southern blot or polymerase chain reaction technique; or (4) a chromosomally abnormal T-cell clone. For staging purposes, it is proposed that these criteria define the B2 blood rating and that the B2 rating be considered equivalent to nodal involvement.
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