ABSTRACT
BACKGROUND: Sometimes, the clinical distinction between early-stage mycosis fungoides and benign inflammatory deimatoses such as psoriasis and dermatitis can be difficult, and it is not uncommon for the histological changes to be non-diagnostic in early-stage mycosis fungoides. Aberrant immunophenotypic expression of T cells occurs frequently in mycosis fungoides, but is uncommon in benign dermatosis. OBJECTIVE: We investigated the distribution and relative numbers of T lyinphocytes and epidermal cells labelled with various monoclonal antibodies in mycosis fungoides, psoriatic, and eczematous lesions by the immunoperoxidase technique. METHODS: Lesional skin tissues were obtained from 7 mycosis fungoides(10 tissues), 9 psoriasis, and 9 eczema patients. Immunohistochemical staining was done on the frozen sections using a labelled streptavidin-biotin-peroxidase complex method with primary antibodies against CD3, CD4, CD5, CD7, CD8, Leu-8, and HLA-DR. RESULTS: The infiltrating cells in mycosis fungoides, psoriatic, and eczematous lesions were uniformly stained with anti-CD3 and most of CD3+ T cells were also stained with anti-CD4. CD 7 expression of T cells was decreased predominantly in mycosis fungoides but loss of CD7 expression was not prominent in psoriatic and eczematous lesions. In the epidermis, HLA-DR was stained extensively in keratinocytes of mycosis fungoides, but only focal staining of HLA-DR was seen in psoriatic and eczematous lesions. CONCLUSION: These findings suggest that CD4+, CD7- T cells and HLA-DR expression of keratinocytes participate in the development of mycosis fungoides, and are helpful in differentiating mycosis fungoides from psoriasis and eczema.