Altered p53 expression and epidermal cell proliferation is seen in vulval lichen sclerosus

Aberrant p53 immunoreactivity has been found in skin pre-malignancies and dysplasias such as Bowen's disease and actinic keratoses. Vulval lichen sclerosus (LS) has been reported to be pre-malignant, with an association of vulval carcinoma in 3% to 6% of patients. In contrast, non-genital LS appears to have no malignant potential. In this immunocytochemical study, we investigated p53 expression in 10 cases of histologically proven vulval LS and 9 cases of non-genital LS using the murine monoclonal antibody Do-1 raised against recombinant human p53 which reacts with both wild-type and mutant p53. None of the vulval specimens had epithelial dysplasia or malignancy. Normal vulval (7 cases) and non-genital skin (5 cases) were used as tissue controls, respectively. The cell proliferation index was also studied using the MIB 1 monoclonal antibody which detects the cell-cycle associated Ki-67 antigen. The technique of microwave irradiation for antigen unmasking was employed on formalin-fixed and paraffin-embedded tissues. There was a significant increase in p53 immunoreactivity in vulval LS (32.13 +/- 15.11 epidermal cells per 100 basal cells) compared to normal vulval skin (7.52 +/- 5.04 epidermal cells per 100 basal cells) (p < 0.001), whereas the MIB 1 labelling index was lower in vulval LS (39.45 +/- 15.88 epidermal cells per 100 basal cells) than in normal controls (86.26 +/- 32.31 epidermal cells per 100 basal cells) (0.001 < p < 0.01). In contrast, there was no significant difference in p53 immunoreactivity or MIB 1 labelling index between non-genital LS and normal controls.(ABSTRACT TRUNCATED AT 250 WORDS)