Immunostaining to identify nuclear antigen provides a convenient way of assessing proliferative kinetics in hyperplastic/tumor tissue.

The object of this study is to find out whether there are any differences in the expression of proliferation related protein among psoriasis, basal cell carcinoma and squamous cell carcinoma by immunohistochemical evaluation on the PCNA (proliferative cell nuclear antigen) and Ki-67.

The detection of PCNA and Ki-67 were done by,immunohistochemical methods (avidin-biotin immunoperoxidase methods) using respective monoclonal antibodies in the paraffin embeded tissues from psoriasis (17 cases), basal cell carcinomas (15 cases) and squamous cell carcinomas (10 cases).

The labelling indices of PCNA were 14.2±4.0% in psoriasis, 10.9±5.5% in basal cell cardinoma and 28.0±7.8% in squamous cell carcinoma, while the labelling indices of Ki-67 were 15.7±3.8% in psoriasis, 11.26.1% in basal cell carcinoma and 30.3±9.4% in squamous cell carcinoma.

1. Interpretation of Ki-67 staining was easier than that for PCNA, mainly because cell morphology was better preserved and the distinction between hyperplastic/tumor and nontumor cell was clear.

2. PCNA and Ki-67 counts had strong correlation to each other (r=0.979).

3. Our immunohistochemical results of PCNA and Ki-67 suggested that proliferative activity was more marked in psoriasis than basal cell carcinoma.