Keratoacanthomas, squamous cell carcinomas, and squamous papillomas were induced in the skin of rabbits and rats with 7,12-dimethylbenz(a)anthracene. Antigenic patterns in these lesions were assessed by indirect immunofluorescence using (a) pemphigus vulgaris sera, which stain specifically the intercellular areas and cell membranes of stratified squamous epithelium, and (b) bullous pemphigoid sera, which react specifically with the basement membrane zone of stratified squamous epithelium. Keratoacanthomas showed normal intercellular immunofluorescence and the basement membrane staining was intact but frequently thickened. Squamous cell carcinomas mainly showed diminished or absent immunofluorescent staining with both sera, whereas squamous papillomas showed normal staining patterns. These findings support previous observations of depletion of tissue-specific antigens in malignant neoplasia. The excessive bullous pemphigoid antigen observed in the keratoacanthoma may reflect the hyperplastic activity of this lesion. Histological assessment of the basement membrane using silver impregnation demonstrated fragmentation and loss of basement membrane reticulin in the squamous cells carcinomas and areas of reticulin thickening in the keratoacanthomas. However, the areas of reticulin change did not correlate with altered basement membrane antigenicity and it is likely that the bullous pemphigoid antigen is produced by the overlying epidermis. The differentiation of keratoacanthoma from squamous cell carcinoma on conventional histopathological grounds may be difficult and the epidermal antigen patterns described would provide a useful adjunct to diagnosis.
This work was supported by grants from The National Health and Medical Research Council and The Australian Research Grants Committee.