p53 protein immunoreactivity in fibrohistiocytic tumors of the skin

Abnormal expression of the 53 kDa nuclear phosphoprotein produced by the p53 gene is observed in many human cancers. p53 nuclear immunoreactivity is found commonly in tumor cells. Immunohistochemistry was performed using a monoclonal antibody, DO-7 (DAKO, Denmark; cat. no. M7001; 1:100 dilution), to investigate p53 protein immunoreactivity in a group of cutaneous fibrohistiocytic tumors that are known to be locally aggressive. The study group consisted of dermatofibrosarcoma protuberans (DFSP) (n = 14) and atypical fibroxanthoma (AFX) (n = 7). Cases of dermatofibroma (DF) (n = 16) formed the benign control group. Intense nuclear immunostaining for p53 protein was observed in 71% of DFSP and 86% of AFX. None of the dermatofibromas showed strong p53 nuclear immunostaining. Statistical analyses revealed significant differences in p53 immunoreactivity between DFSP and DF (P = 0.0001, chi 2 test) and between AFX and DF (P = 0.0001, chi 2 test). In conclusion, increased p53 protein immunoreactivity is found in DFSP and AFX but not in DF. These differences in p53 immunoreactivity suggest that increased expression of the protein may be important in the pathogenesis of the more aggressive group of fibrohistiocytic tumors.