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 histo logical grade and tobacco smoking. Method--Paraffin wax embedded tissu e sections from 41 cases of invasive SCC of the larynx, 28 cases of dy splasia and 14 control laryngeal biopsy specimens were studied immunoh istochemically using two anti-p53 monoclonal antibodies (DO7 and 1801) . The Streptavidin/horseradish peroxidase method was used after microw ave antigen retrieval and a semiquantitative method was applied to ass ess the extent of p53 expression. Results--Of the cases of invasive SC C of the larynx, 78% (32/41), regardless of histological grade, overex pressed p53 compared with only 30% (eight of 28) of cases of mild dysp lasia. A gradual increase in p53 expression from mild to severe dyspla sia (60%) was observed, and only three of 14 control biopsy specimens of laryngeal nodules showed occasional weakly positive basal cells. Co nclusion--The gradual increase in p53 expression from mild to severe d ysplasia to invasive SCC indicates that p53 overexpression is an early event in laryngeal carcinogenesis which may lead to invasive malignan cy. p53 overexpression may be related to environmental factors as most of the patients smoked tobacco. Microwave postfixation may be essenti al for the reliable detection of p53.