Expression of TGF-Alpha and c-fos in Conventional and Basaloid Squamous Cell Carcinoma of Floor of Mouth

Abstract

Basaloid squamous cell carcinoma of the floor of the mouth is a newly recognized variant of squamous cell carcinoma that has a very aggressive behavior. To characterize basaloid squamous cell carcinoma at the molecular level, the authors studied the immunohistochemical expression in this tumor of the oncogene c-fos and of transforming growth factor-alpha. Eight cases of basaloid squamous cell carcinoma were evaluated by immunoperoxidase staining and compared to 16 squamous cell carcinomas of the floor of the mouth that ranged from well to poorly differentiated. The expression of c-fos was stronger in basaloid squamous cell carcinoma and poorly differentiated squamous cell carcinoma than it was in well-differentiated squamous cell carcinoma. Conversely, transforming growth factor-alpha expression was much stronger in well-differentiated squamous cell carcinoma than in basaloid squamous cell carcinoma or poorly differentiated squamous cell carcinoma. Moderately differentiated squamous cell carcinomas showed weak to moderate immunostaining for transforming growth factor-alpha but stained intensely for c- fos, which was consistently expressed at a high level in these tumors. This study confirms the poorly differentiated nature of basaloid squamous cell carcinoma, which has a similar pattern of staining as poorly differentiated. The decreased expression of transforming growth factor-alpha in basaloid squamous cell carcinoma may be related to the low degree of differentiation of this tumor since transforming growth factor-alpha tends to have higher levels of expression in well-differentiated tumor cells. Int J Surg Pathol 3(3):169-174, 1996