The use of immunohistologic analysis in differentiating cutaneous T-cell lymphoma from psoriasis and dermatitis

--Many investigators have applied immunohistologic analysis to skin biopsy specimens to distinguish cutaneous T-cell lymphoma (CTCL) from benign inflammatory diseases, such as psoriasis and dermatitis, which can clinically mimic early-stage CTCL. We studied the number and distribution of epidermal cells labeled with various monoclonal antibodies in normal skin and in psoriatic, dermatitic, and CTCL lesions by the immunoperoxidase technique.

--Extensive staining of keratinocytes (KCs) with HLA-DR was seen in 27 of 41 patients with CTCL, but in only one of 14 patients with psoriasis and zero of 10 patients with dermatitis. CD2+ and CD3+ cells were present in the middle and upper epidermis of CTCL lesions in much greater numbers than in normal, dermatitic, and psoriatic skin. The percent epidermal area covered by CD1+ cells in psoriatic lesions (1.13%) and dermatitic lesions (1.65%) was significantly lower than that found in CTCL lesions (3.60%).

--Epidermal immunohistologic patterns using anti-CD1, anti-CD2, anti-CD3, and anti-HLA-DR antibodies have the potential to distinguish CTCL from psoriasis and dermatitis in clinically ambiguous cases.