There are clinical and histopathological similaritie between lichen planus (OLP) and oral lichenoid reactions (OLL) but they have different treatment approaches. The present study examined the correlation between clinical and histopathological findings in lichen planus and oral lichenoid reaction based on modified WHO diagnostic criteria in order to evaluate using these criteria in differentiating these lesions.

In this retrospective descriptive study, information, including clinical characteristics, age, sex, and histopathological characteristics were extracted from the clinical records of 101 OLP cases and 49 OLL cases. The paraffin block of biopsies was removed from the archives in pathology department and the prepared incision was stained with hematoxylin-eosin. The slides were examined by a pathologist and histopathological characteristics were recorded in a checklist. Data were analyzed by descriptive statistics, kappa score, Chi-square, and independent sample t-test.

According to the 1978 diagnostic criteria, the agreement between clinical and histopathological diagnosis was 98.79% in OLP and 69.57% in OLL (P<0.001). According to the Modified WHO diagnostic criteria, the agreement between clinical and histopathological diagnosis was 99% in OLP and 71.43% in OLL (P<0.001).

In diagnosis of lichen planus and oral lichenoid reaction, there is a higher clinicopathologic correlation based on the modified WHO diagnostic criteria compared with the 1978 diagnostic criteria. Therefore, it is suggested to be used in clinical and histopathological investigations.