ABERRANT ACCUMULATION OF P53 ASSOCIATES WITH KI67 AND MITOTIC COUNT IN BENIGN SKIN-LESIONS

Sixty-two skin samples from patients with a variety of benign disorder s (20 cases of psoriasis, 14 cases of chronic dermatitis, 11 seborrhoe ic keratoses, 11 cases of lichen planus), and seven normal skin sample s, were stained immunohistochemically with a polyclonal antibody (CM-1 ) to p53, and a monoclonal antibody to Ki67, using the avidin-biotin c omplex method, p53-positive keratinocytes could be found in most of th ese lesions. The percentage of p53-positive cells was, however, far lo wer than usually seen in p53-positive malignant tumours. No p53 reacti vity was observed in the normal skin samples. Variable Ki67 reactivity was observed in all skin samples. Overall, the number of Ki67-positiv e cells was higher in skin samples in which the proportion of p53-posi tive cells was high (> 0.5% of total epidermal cell population) (P = 0 .004). This also applied separately to psoriatic and non-psoriatic les ions (P = 0.028 and P = 0.033, respectively). In cases with > 10% of K i67-positive cells, there were significantly more mitoses (P < 0.001). This association applied to both psoriasis and the other lesions stud ied (P = 0.024 and P < 0.001, respectively). The results show that imm unohistochemically detectable accumulation of p53 is a frequent findin g in non-neoplastic skin lesions. As p53 positivity was associated wit h the proliferation marker Ki67, the accumulation of p53 is possibly a response to an increased proliferation rate of the keratinocytes in t hese skin diseases, or alternatively it may be associated with apoptos is.