Malignant spiradenomas (spiradenocarcinomas) are exceedingly rare tumours of cutaneous adnexal origin, consisting of two components: benign--the pre-existent adenoma, and malignant--developing from the former part. We studied p53 protein expression in both compartments of three cases of malignant spiradenoma and compared these results with results obtained with eight cases of spiradenoma. Nuclear staining was consistently negative in all benign tumours, whilst in the cases of malignant transformation within spiradenoma p53 protein was present in the carcinomatous component, but the immunostaining remained negative in the benign counterpart of the tumour. In the zone of transition between both components of the spiradenocarcinomas p53 expression was positive in the cells with morphological atypia, providing clear discrimination. Thus, we conclude that the accumulation of p53 protein, which results from alterations in its turnover, accompanies the process of malignant transformation within long-standing spiradenomas.