P53 OVEREXPRESSION IN LARYNGEAL SQUAMOUS-CELL CARCINOMA AND DYSPLASIA

Aim--To investigate the expression of p53 protein in invasive squamous cell carcinoma (SCC) of the larynx and dysplasia in relation to histological grade and tobacco smoking. Method--Paraffin wax embedded tissue sections from 41 cases of invasive SCC of the larynx, 28 cases of dysplasia and 14 control laryngeal biopsy specimens were studied immunohistochemically using two anti-p53 monoclonal antibodies (DO7 and 1801). The Streptavidin/horseradish peroxidase method was used after microwave antigen retrieval and a semiquantitative method was applied to assess the extent of p53 expression. Results--Of the cases of invasive SCC of the larynx, 78% (32/41), regardless of histological grade, overexpressed p53 compared with only 30% (eight of 28) of cases of mild dysplasia. A gradual increase in p53 expression from mild to severe dysplasia (60%) was observed, and only three of 14 control biopsy specimens of laryngeal nodules showed occasional weakly positive basal cells. Conclusion--The gradual increase in p53 expression from mild to severe dysplasia to invasive SCC indicates that p53 overexpression is an early event in laryngeal carcinogenesis which may lead to invasive malignancy. p53 overexpression may be related to environmental factors as most of the patients smoked tobacco. Microwave postfixation may be essential for the reliable detection of p53.