Background and Aim: Oral mucosal lesions have various prevalence rates among different populations. Few studies have evaluated the frequency of oral mucosal lesions in Iranian population. This study aimed to determine the frequency of oral mucosal lesions and the related factors.

Materials and Methods: This descriptive study was conducted based on the data in the archives of two referral centers, including the Pathology Departments of the Cancer Institute of Imam Khomeini and Buali hospitals in Tehran, from June 2000 to July 2014. Age, sex, location of the lesions and microscopic diagnosis were retrieved from the files, and the data were analyzed by SPSS13 using Chi-square test. 

Results: Among 59273 files, 976 patients (1.56%) had oral mucosal lesions, and the most prevalent pathologies were epithelial lesions (89.4%), followed by connective tissue lesions (6.5%). Squamous Cell Carcinoma (53%) was the most prevalent epithelial lesion. The most common location of oral mucosal lesions was the lips (27.8%). Mean age of the patients was 44 ± 3 years. The incidence of mucosal lesions increased with age, while no correlation was observed between mucosal lesions and sex (P<0.9).

Conclusion: The most prevalent oral mucosal lesion was the Squamous Cell Carcinoma, which is a malignant tumor with epithelial origin, and its early diagnosis is necessary.