Aberrant accumulation of p53 associates with Ki67 and mitotic count in benign skin lesions

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Abstract
Sixty-two skin samples from patients with a variety of benign disorders (20 cases of psoriasis, 14 cases of chronic dermatitis, 11 seborrhoeic keratoses, 11 cases of lichen planus), and seven normal skin samples, were stained immunohistochemically with a polyclonal antibody (CM-1) to p53, and a monoclonal antibody to Ki67, using the avidin-biotin complex method, p53-positive keratinocytes could be found in most of these lesions. The percentage of p53-positive cells was, however, far lower than usually seen in p53-positive malignant tumours. No p53 reactivity was observed in the normal skin samples. Variable Ki67 reactivity was observed in all skin samples. Overall, the number of Ki67-positive cells was higher in skin samples in which the proportion of p53-positive cells was high (>0.5% of total epidermal cell population) (P=0.004). This also applied separately to psoriatic and non-psoriatic lesions (P=0.028 and P=0.033, respectively). In cases with >10% of Ki67-positive cells, there were significantly more mitoses (PP=0.024 and P <0.001, respectively). The results show that immunohistochemically detectable accumulation of p53 is a frequent finding in non-neoplastic skin lesions. As p53 positivity was associated with the proliferation marker Ki67, the accumulation of p53 is possibly a response to an increased proliferation rate of the keratinocytes in these skin diseases, or alternatively it may be associated with apoptosis.