P53 PROTEIN EXPRESSION IN SEQUENTIAL BIOPSIES OF ORAL DYSPLASIAS AND IN-SITU CARCINOMAS

Immunohistochemically detectable levels of p53 may be seen early in th e malignant transformation of some neoplasms. To determine if p53 is i mmunocytochemically detectable, and therefore presumptively abnormal, in oral dysplasias and in situ carcinomas, and to explore the natural history of p53 protein expression in these lesions, sequential biopsie s from patients with lesions occurring in the same anatomic site were examined. Formalin-fixed, paraffin-embedded sections from 19 patients were evaluated immunohistochemically for p53 protein using antibody cl ones Pab1801 and BP53-12. With two exceptions, comparable results were observed with these antibodies. p53 protein was detected immunocytoch emically in 6 of 13 patients with dysplasias; 3 of these progressed to p53-positive invasive carcinoma, one advanced to a more severe grade of p53-positive dysplasia, one developed into a p53-negative verrucous carcinoma, and one represented a p53-positive dysplasia developing fi ve years after treatment of a p53-positive carcinoma. The p53-positive dysplasias, which were found in all subtypes (mild, moderate, severe) , preceded histologic malignant change by months to years. p53 detecti on was evident in 4 of 6 patients with in situ lesions. Sequential bio psies of three of these lesions showed no change in lesion histology o r p53 staining, and one lesion advanced to a p53-positive carcinoma. I t is concluded that p53 protein may be detected early in the developme nt of a subset of p53-positive oral squamous cell carcinomas. This phe nomenon may be seen in dysplasias and in situ lesions, and it may have prognostic implications.