c-myc oncoprotein expression in oral precancerous and early cancerous lesions.

Squamous cell carcinoma of the oral cavity is often preceded by clinically evident precancerous lesions. These lesions exhibit progressive cytomorphologic changes connoting cellular transformation to malignant neoplasia. Molecular events underlie the microscopically identifiable cytological changes that herald transformation. Various proto-oncogenes are activated, overexpressed or mutated in the process of transformation. This investigation was designed to determine whether the nuclear binding c-myc oncoprotein, an activator of cell division, parallels or precedes cytomorphological changes at various histologically defined stages in oral precancerous lesions. Employing immunohistological methods, it was determined that c-myc nuclear labelling paralleled the progressive histological changes among various stages of transformation. It was also noted that some, yet not all, instances of benign keratoses which lacked any cytologic evidence of atypia harboured c-myc oncoprotein positive nuclei. It is concluded that c-myc expression is correlated with progressive cell transformation in oral cancerous lesions.