Differential hybridization analysis was used to identify molecular differences between a relative benign and a highly aggressive rat prostatic tumor derived from the Dunning R-3327-H adenocarcinoma. From the several differentially expressed mRNAs identified, we here report the characterization of pBUS51 which encodes a transcript highly expressed in all-anaplastic Dunning tumors. Only a very low expression was detectable in normal rat prostate or in the differentiated tumors of the Dunning system. Nucleotide sequence analysis and computer-assisted database comparison revealed that pBUS51 was highly homologous to vimentin and therefore likely the rat homolog of this protein.