Keratoacanthoma development in the PD mice.

<p>Chemical carcinogenesis study in heterozygous PD and wild-type littermates. A. Papilloma formation in a PD heterozygote during TPA treatment shows no difference between experimental and control groups of mice. B. Clinical appearance of a typical papilloma. C. PD heterozygous mouse that has developed a typical keratoacanthoma showing a keratinaceous core and well-defined tumor. D. Histologic examination of keratoacanthomata from PD heterozygous mice showing classic appearance of these tumors. E. Mutational analysis of PD mice for <i>Hras</i> codons 12,13,61 and <i>Tp53</i>.