Transforming growth factor alpha expression helps to distinguish keratoacanthomas from squamous cell carcinomas

Keratoacanthomas may be difficult to distinguish histologically from squamous cell carcinomas. We studied 20 keratocanthomas and 22 squamous cell carcinomas immunohistochemically using an antibody directed against transforming growth factor alpha to determine if the pattern of transforming growth factor alpha expression would provide a useful method of differentiating these tumors. Ninety percent of the keratoacanthomas demonstrated a diffuse pattern within tumor lobules in which all but the most peripheral rim of cells were stained. A similar localization of transforming growth factor alpha was not identified in squamous cell carcinomas. In addition, 40% of the squamous cell carcinomas but none of the keratoacanthomas showed focal transforming growth factor alpha immunostaining. Our results suggest that transforming growth factor alpha expression may be a marker of epithelial differentiation and may help distinguish between these two tumors.