A Survey on Orbital Space-Occupying Lesions during a Twelve-Year Period from a Referral Center in Iran.

Purpose: In this study, we describe different orbital space-occupying lesions (SOLs) from a referral center in Iran.

Methods: In this retrospective case series, all records of "orbital tumors" with a definite histopathologic diagnosis at a referral center in Iran were reviewed from April 2008 to May 2020.

Results: A total of 375 orbital SOLs were included. The study population consisted of 212 (56.5%) female and 163 (43.5%) male subjects with overall mean age of 31.09 $\pm$ 21.80 years. The most common clinical presentation was proptosis and the superotemporal quadrant was the most frequent site of involvement. Extraconal lesions (276 cases, 73.6%) outnumbered intraconal lesions (99 cases 26.4%). The great majority of SOLs (344, 91.7%) were primary, while 24 (6.4%) were secondary and 7 (1.9%) were metastatic. Benign lesions (309, 82.4%) were much more common than malignant SOLs (66, 17.6%). Overall, dermoid cysts and malignant lymphoma were the most prevalent benign and malignant orbital SOLs, respectively. The malignant to benign lesion ratio was 0.46 in children ($\le$18 years), 0.81 in middle-aged subjects (19-59 years), and 5.9 in older ($\ge$60 years) cases. The most common type of malignancy was rhabdomyosarcoma in children, lymphoma in middle-aged subjects, and invasive basal cell carcinoma in older age group.

Conclusion: Over the 12-year study period, benign, primary, extraconal orbital SOLs were more frequent than malignant, secondary, and intraconal lesions. The ratio of malignant lesions increased with age in this cohort of patients.