History of Breast Cancer in Patients with Oral Lichen Planus: A Case-Control Study.

: The purpose of this study was to determine the association between oral lichen planus (OLP) and the history of cancer outside of oral cavity and the predominance of its location. : This case-control study included 600 OLP patients and 600 control subjects evaluated in the same section, matched for age and sex to the OLP patients. OLP patients were diagnosed clinically and histologically. Initially, the prevalence of the most frequent types of cancers was described. A Pearson chi-squared test model was used to determine the association of cancer history and OLP. It was considered statistically significant whether value was ≤0.05. The final multivariate regression model was built after applying a backward selection method to the complete multivariate model considering the odds ratio (OR) with a 95% confidence interval (CI). : The history of cancer was significantly associated with OLP regardless of age, sex, tobacco and or alcohol use in both univariate [OR = 2.26 (95%CI: 1.26-4.24); = 0.008] and multivariate analyses [OR = 2.21 (95%CI: 1.21-4.19); = 0.012]. According to the location of cancer, there was an association between OLP and history of breast cancer [OR = 3.71 (95%CI = 1.03-13.38); = 0.032]. : This case-control study suggests a higher frequency of cancer, particularly breast cancer, among patients with OLP compared to the control group. Due to the study's design and sample limitations, these findings should be interpreted cautiously. Future longitudinal, multi-institutional studies with rigorous control for cancer history and other confounding factors are essential to further explore the association between OLP and cancer, particularly breast cancer.