DNA content, Cyclooxygenase-2 expression and loss of E-cadherin expression do not predict risk of malignant transformation in oral lichen planus

Oral lichen planus (OLP) may be associated with a small risk of malignant transformation of the oral mucosa. Using cases which had transformed, and those which had not, this study aimed to evaluate the potential of DNA content, expression of Cyclooxygenase-2 (Cox-2) and of epithelial (E)-cadherin as risk markers in lesions of OLP. We investigated 78 archival biopsies from; (1) 26 OLP patients with at least two biopsies, of whom seven presented OLP with epithelial dysplasia, followed by oral squamous cell carcinoma (OSCC) in five of them, (2) 19 OLP patients with one biopsy taken. Image cytometry for measurement of DNA content and immunohistochemistry for visualisation of Cox-2 and E-cadherin expression were performed. All OLP biopsies investigated were classified as diploid, one OLP with epithelial dysplasia was tetraploid and all OSCC were diploid. Cox-2 was detected in the epithelium of all OLP specimens investigated, as well as in epithelial dysplasias and OSCC. Focal loss of E-cadherin expression was observed in basal keratinocytes in 88% of the OLP specimens investigated, in all epithelial dysplasias and OSCC. In conclusion, neither aneuploidy, Cox-2 expression, nor loss of E-cadherin expression, were significant reliable markers to select OLP lesions at risk for development of OSCC in the present patient material.