Ki67 expression in lichen sclerosus of vulva in patients with and without associated squamous cell carcinoma

Aims: To investigate the malignant potential of lichen sclerosus, a study using the cell proliferation marker Ki67 comparing lichen sclerosus with and without associated squamous cell carcinoma was performed, Methods and results: Formalin-fixed, paraffin-embedded slides of 13 cases of lichen sclerosus with associated carcinoma, and 31 cases without associated carcinoma, including 16 random cases, seven with epidermal thickening and eight with epidermal thinning, were examined by the immunoperoxidase technique for Ki67, a cell proliferation marker. Ki67 reactivity was mostly seen in the basal and parabasal cells in both groups of lichen sclerosus and this pattern was similar to normal skin. squamous cell hyperplasia and analogous to that of one form of squamous cell carcinoma. There was a mean of 50 Ki67 positive cells per 100 basal cells in lichen sclerosus with associated squamous cell carcinoma; however, in squamous cell hyperplasia adjacent to carcinoma this rose to 90 Ki67 positive cells per 100 basal cells. In lichen sclerosus without associated carcinoma, the random cases had a count of 53 per 100 basal cells, those with epidermal thickening 53 and those with thinning 42. Non-genital normal skin had a count of 71 per 100 basal cells. Conclusion: The lack of qualitative differences of Ki67 expression in normal skin, in lichen sclerosus with and without carcinoma, in squamous cell hyperplasia and in one form of squamous cell carcinoma indicates that these conditions share a common localized pattern of cell proliferation and does not support or deny the malignant potential of lichen sclerosus, The higher Ki67 count in squamous cell hyperplasia adjacent to carcinoma could indicate premalignancy or a reaction to the carcinoma. In patients without carcinoma, the higher Ki67 count in thickened lichen sclerosus compared to thinned suggests that some or all of the cases of thickened lichen sclerosus were lichen sclerosus with squamous cell hyperplasia or that lichen simplex chronicus superimposed on lichen sclerosus has a higher Ki67 expression or that the distinction between squamous cell hyperplasia and lichen simplex chronicus is only one of terminology.