Markedly diminished epidermal keratinocyte expression of intercellular adhesion molecule-1 (ICAM-1) in Sézary syndrome.

In mycosis fungoides the malignant T cells express lymphocyte function-associated antigen-1, which allows them to bind to epidermal keratinocytes expressing the gamma interferon-inducible intercellular adhesion molecule-1. In this report, a patient with leukemic-stage mycosis fungoides (Sézary syndrome) had widespread erythematous dermal infiltrates containing malignant T cells, but without any epidermotropism. We discovered that the T cells expressed normal amounts of functional lymphocyte function-associated antigen-1, but the keratinocytes did not express significant levels of intercellular adhesion molecule-1, which was probably due to the inability of the malignant T cells to produce gamma interferon. These results support the concept that the inability of malignant T cells to enter the epidermis may contribute to emergence of more clinically aggressive T-cell clones that are no longer confined to the skin, but infiltrate the blood, lymph nodes, and viscera, as is seen in Sézary syndrome.