A retrospective multi-institutional study on the clinical categorization and diagnosis of oral lichen planus

Objective Oral lichen planus (OLP) displays various and complicated clinical presentations which often make their differential diagnosis challenging, and thus helpful clinical practice guidelines for the diagnosis and treatment of OLP have been long awaited. Methods The Japanese OLP Working Group (OLP-WG) has collected and analyzed a total of 393 OLP cases provided by 48 institutions nationwide from 2009 to 2011 toward the establishment of valuable clinical practice guidelines for OLP. Collected samples were classified according to their original diagnoses into three groups: bilateral reticular (Group 1); bilateral atrophic/erosive (Group 2); and unilateral (Group 3) buccal lesions. Ten OLP-WG members used intraoral pictures to categorize the cases into Andreasen's six types, and then examined the biopsy specimens to make pathological and comprehensive diagnoses. Results When Andreasen's reticular, plaque, and papular types were sorted into white (W) type, and when atrophic, erosive, and bullous types were sorted into red (R) type, they formed six clusters based on the number of the members’ judgments: W1 (W dominant), W/R (W-R competing), R1 (R dominant), UD (undeterminable dominant), W2 (boundary), and R2 (boundary). Both in the bilateral and unilateral lesion groups, proportions of cases which were comprehensively diagnosed as OLP were significantly higher in cluster W1 than those in cluster R1 (p<0.01). A considerable percentage of lesions likely judged as R were diagnosed as OLL or other than OLP. Conclusions These results indicated that the simple W or R classification would be a better substitute for Andreasen's in the clinical categorization of OLP.