Clinical Features:

• The leukemic phase of mycosis fungoides, with a worse prognosis than MF
• Pruritic erythroderma with scaling and edema, palmoplantar hyperkeratosis, alopecia, onychodystrophy and lymphadenopathy
• Advanced cases may show widespread infiltration of the face, leading to leonine facies.

Histologic Features:

• Usually a relatively nonspecific perivascular or band-like upper dermal infiltrate of small lymphocytes, which may or may not display atypia (e.g., cerebriform nuclei)
• Epidermotropism is present in only 40% of cases.
• The skin findings are indistinguishable from the patch or plaque stage of mycosis fungoides.
• Lymph nodes may show only dermatopathic lymphadenopathy or may show frank involvement with effacement of nodal architecture by lymphocytes with cerebriform nuclei.
• The immunophenotype is identical to that of mycosis fungoides (helper T-cell phenotype): CD2+, CD3+, CD4+, CD5+, CD8-, CD30-.
• Diagnosis requires the demonstration of over 1000 circulating Sézary cells per cubic millimeter in the peripheral blood with a CD4:CD8 ratio of over 10 to 1.