Introduction
Oral lesions can affect people’s quality of life by interfering with chewing, swallowing and speech [1, 2]. These lesions are originated from epithelial or mesenchymal tissues. Oral lesions may be non-proliferative (e.g. inflammatory diseases) or proliferative (neoplastic) which can be benign or malignant [3, 4]. Malignant oral lesions are mainly derived from epithelial tissues and can cause life-threatening diseases. Oral cancers are more common in male patients because of some risk factors such as smoking, alcohol use, and sun exposure [3, 4, 5, 6]. Epidemiological data about the benign and malignant oral lesions in Asia including Iran is limited [7, 8, 9, 10]. The present study aims to investigate the frequency of oral lesions in Rasht, Iran based on histopathologic studies.
Methods
In this cross-sectional study, histopathologic data of oral lesions were collected from the medical records in Razi laboratory, Rasht, northern Iran from 2015 to 2019 were evaluated which included: Patients’ age and sex, histopathologic findings, location of the lesions, type of lesions, and origin of lesions. Non-specific diagnoses, and dental and bone lesions were excluded. For patients with multiple biopsies, only one biopsy with definite diagnosis was included. Data were analyzed in SPSS software, version 18. A P<0.05 was statistically significant. Quantitative variables were described using mean and standard deviation and qualitative data were described using number and percentage. Fisher’s exact test was used to compare the variables. 
Results
A total of 259 reports related to oral cavity lesions were included in this study. The patients aged 1-89 years (Mean age: 52.09±19 years), and 40.2% were male. It was found that 26.3% of oral lesions were non-proliferative while 73.7% were proliferative. Among proliferative lesions, 45.9% were benign, 4.6% were premalignant and 23.2% were malignant. The oral lesions in patients aged <40 years were mainly benign (64.2%), whereas those in patients >70 years were mostly malignant. Tongue was the most common location for the lesions (34.7%) and also for the malignant lesions (46.7%). 27.5% of all tongue lesions were malignant. Benign lesions were significantly higher in females, while malignant lesions were significantly higher in males (P=0.011). Epithelial tissues were the most common site of origin (49%) and salivary glands were the least common site of origin (11.6%) for oral lesions. The most common benign lesion was mucosal fibroma and the most common malignant lesion was squamous cell carcinoma. 
Lesions originated from epithelial tissues were malignant in 43.3% of cases. Non-epithelial lesions were malignant in 4.9% of cases. All lesions from salivary glands were benign. This difference was significant based on the results of Fisher exact test (P<0.001).
Discussion
It was found that tongue, lip, and buccal mucosa were the most common locations for oral lesions, which is consistent with the results of previous studies. Malignant lesions were more common on the tongue of patients in previous studies which is consistent with our findings [5, 6, 7, 8]. Therefore, attention to the tongue lesions is very important. Kamble et al and Do et al. reported a lower frequency of malignant lesions on the tongue because their studies were performed by clinical examination of normal population. They did not study histopathologic reports of oral lesions which is usually done when there is a clinical suspicion of malignancy [7, 9]. Al-Mobeeriek et al. screened normal population for oral lesions and observed lower frequency of oral lesion in older patients which is not in agreement with our results [5]. 
El Toum et al. reported that the frequency of oral lesions increased with aging and benign lesions were more frequent in young patients [8] which is consistent with our results. 
Jahanbani et al. and Shahsavari et al. reported that the most of oral lesions were derived from epithelial tissues and the most common lesion was squamous cell carcinoma [6, 10]. In our study, mucosal fibroma was the most common benign lesion which is usually a reactive hyperplasia caused by chronic irritations or rarely a benign cellular proliferation [11]. Aljazaeri, et al. reported pyogenic granuloma as the most common benign oral lesion [4]. Its low frequency in our study may be due to the lack of cooperation of the center for sending the samples of pyogenic granuloma for pathologic evaluation. In most of previous studies, oral malignancies were more frequent in men rather than in women , which is consistent with our results. It can be due to more exposure of men to carcinogenic factors. 
The present study had some limitations including sample size was small, high number of non-specific histopathologic reports, and no clinical examination of participants. 
In conclusion, malignant oral lesions are more common in men aged >70 years, where the tongue is the most common site and is mainly derived from epithelial tissues.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Guilan University of Medical Sciences (Code: IR.GUMS.REC.1399.577).

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Study concept and design: Narges Alizadeh, Maryam Rabiei, Amirreza Sayyar; Acquisition, analysis, or interpretation of data: Rana Rafiei, Amirreza Sayyar; Drafting the manuscript: Rana Rafiei, Amirreza Sayyar and Nooshin Zaresharifi; Critical revision of the manuscript for important intellectual content: Rana Rafiei, Narges Alizadeh, Amirreza Sayyar, Nooshin Zaresharifi; Statistical analysis: Rana Rafiei, Habib Eslami; Administrative, technical or material support: Deputy of Research and Technology of Gilan University of Medical Sciences; Supervision: Narges Alizadeh, Maryam Rabiei.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank the Vice-Chancellor of Research and Technology of Guilan University of Medical Sciences.


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