Immunohistochemical study of p53 protein expression in Spitz nevus as compared with other melanocytic lesions.

The accumulation of p53 protein was studied immunohistochemically on paraffin-embedded sections of 26 Spitz nevi (SNs), 26 primary invasive cutaneous malignant melanomas (MMs), 20 metastases of MM, and 17 ordinary compound nevi (CNs), using monoclonal antibody BP53-12. Positive reactivity was detected in some of the tumor cells in seven (35%) metastatic MMs, all exhibiting strong nuclear staining; eight (31%) primary MMs, of which seven showed strong nuclear staining; two (7%) SNs, of which only one showed strong nuclear staining; and none of the CNs. The frequencies of the positively stained lesions in general, and the strongly positively stained lesions in particular, in the MM and metastatic MM groups were each statistically significantly higher than the respective frequencies in the SN and CN groups. We believe that the immunohistochemical detection of p53 protein with the use of monoclonal antibodies such as BP53-12 on paraffin sections, especially when strong nuclear reactivity is demonstrated, may prove to be an adjunctive tool in the histopathologic differentiation of MM from SN.