[Histopathological analysis of oral lichen planus with malignant transformation].

Objective: To estimate the histological features of oral lichen planus (OLP) which underwent malignant transformation and discuss the current problems in OLP pathological diagnosis. Methods: Using the modified WHO OLP criteria (2003), reevaluated the pathological changes of cases diagnosed initially as OLP and transformed into squamous cell carcinomas indicated by subsequent biopsies. Results: Among 3 721 cases of OLP clinically and pathologically diagnosed during 1984 and 2015, there were 19 cases (0.51%) having underwent malignant transformation. Reevaluation of the initial biopsies revealed that 10 cases did not meet the criteria of OLP, as without characteristic basal cell liquefaction, not exhibiting sufficient band-like lymphocytes infiltration, or presenting with epithelial dysplasia. There were 9 cases of OLP malignant transformation left after the reevaluation. Conclusions: Pathological diagnosis of OLP should fully fit the criteria i.e. basal cell liquefaction, typical band-like lymphocytes infiltration and absence of epithelial dysplasia, which is also a prerequisite for researches in malignant transformation of OLP.