Salivary Gland Tumors in Iran: A Systematic Review of 2870 Cases Based on the New WHO Classification

There is no consensus on the prevalence of salivary gland tumors (SGTs) in Iran. Thus, we systematically reviewed the literature about the prevalence of SGTs in Iran and applied the last world health organization (WHO) classification.

The systematic literature search was performed in EMBASE, Scopus, PubMed MEDLINE, Google Scholar, Scientific Information Database (SID), and Magiran; we searched for "salivary gland," "tumor," "prevalence," and "Iran" until 1 March 2021. The studies included were written in the English and Farsi languages. The weighted mean prevalence of SGTs was calculated as prevalence (%) * (N/the sum of all N). We used the unpaired Two-sample T-test to compare the weighted means.

A total of 17 studies, including 2870 patients, were selected for the data synthesis. The weighted mean prevalence of benign and malignant tumors was 66% (95% CI: 59-73) and 34% (95% CI: 27-41), respectively. The patients' mean age was reported in 10 out of the 17 studies. The weighted mean age of the patients was 40 (95% CI: 37-42) and 49 (95% CI: 43-55) years for benign and malignant tumors, respectively (P=0.01). Pleomorphic adenoma (PA), followed by Warthin's tumor (WT), was the most prevalent benign tumor. Moreover, the most common malignant tumors were mucoepidermoid carcinoma (MEC) and adenoid cystic carcinoma (AdCC).

More than one-third of SGTs in Iran were malignant, which is higher than the reports from Middle Eastern countries. Information about risk factors and the burden of SGTs in Iran is insufficient. Thus, further well-designed longitudinal studies are warranted.