Abstract: Objective To investigate the role of immunophenotyping in distinguishing mycosis fungoides (MF) from lichen planus and psoriasis.Methods The expression of CD1a,CD4,CD8,ICAM-1,LFA-1,HLA-DR,CD30 and CD7 was measured by ABC immunohistochemical technique in specimens obtained from lesional skin of 15 cases of MF,17 cases of lichen planus and 17 cases of psoriasis,and in the skin of 6 healthy controls.Results In the lesional epidermis of MF,the density of cells positive for CD1a,CD30 or ICAM-1,was significantly higher (mononuclear cells,P<0.001;dendritic cells,P<0.01) than that in the lesional epidermis of lichen planus,psoriasis and in the skin of healthy controls.The density of cells positive for CD4 or CD8 and of dendritic cells positive for HLA-DR was higher in lesional epidermis of MF than in that of lichen planus.The linear density of CD1a-positive cells (P<0.01),the percentages of cells positive for ICAM-1 (P<0.05) or LFA-1 (P<0.05) were all higher in the lesional dermis of MF than in that of lichen planus.As far as the CD7-positive cell density was concerned,it was higher in the lesional dermis of lichen planus and psoriasis than in that of MF and skin of healthy controls (P<0.01),while no difference was found between the epidermis of MF and that of lichen planus or psoriasis.Conclusion There are differences in the expression of CD1a,CD4,CD8,ICAM-1,LFA-1,HLA-DR,CD30 and CD7 in the lesional skin of MF,lichen planus and psoriasis,which may provide a clue to the pathogenesis of these diseases.

Key words: Mycosis fungoides, Lichen planus, Psoriasis, Immunophenotyping