Diagnosis: Cutaneous T-cell neoplasms
• Mycosis fungoides (MF) and Sézary’s syndrome (SS) are both primary cutaneous T-cell lymphomas that have overlapping features but are distinct clinicopathologic entities.
• MF is an indolent disease with slow progression from patches to plaques to potential tumors of the skin with variable degrees of epidermal infiltration (lichenoid infiltrates to frank epidermotropism with Pautrier microabcesses). Stage is determined by the degree of skin, lymph node, and peripheral blood involvement and is predictive of prognosis.
• SS is a more aggressive disease with generalized erythroderma, lymphadenopathy, and the presence of characteristic Sézary cells. Epidermotropism is often absent. Prognosis is poor, with an overall 5-year survival rate of 10% to 20%.
• Sézary cells are clonally related T cells that have cerebriform nuclei on peripheral blood smear.
• The phenotype of the malignant cells is similar in MF and SS: CD2+, CD5+, CD3+, CD4+, and often loss of CD7.