Immunohistochemical detection of p53 in epidermal proliferations overlying dermatofibromas

Basaloid proliferations of epidermis overlying dermatofibromas and morphologically resembling superficial basal cell carcinomas might possess a malignant potential. In order to elucidate whether these basaloid proliferations share phenotypic characteristics with malignancy, we examined immunohistochemically 19 cases of dermatofibroma with overlying epidermal basaloid proliferations, 10 dermatofibromas with overlying simple epidermal proliferations, and 10 invasive basal cell carcinomas for expression of p53. Simple and basaloid proliferations showed sparse positive immunostaining for p53, as seen in normal epidermis. No differences in staining pattern or number of positive keratinocytes could be demonstrated between these conditions. The dermatofibromas were negative. The invasive basal cell carcinomas showed abundant p53 positivity. The lack of p53 immunoreactivity in the epidermal basaloid proliferations overlying dermatofibromas indicates that these lesions have not acquired a phenotype as seen in malignant conditions.