Clinical Characteristics and Imaging features of Primary Orbital Lymphoma

Objective: To analyze the clinical characteristics and imaging features of primary orbital lymphoma in order to improve early diagnosis of the disease. Methods: Eighty-two patients were recruited from January 2015 to May 2022 who were diagnosed with orbital lymphomas via histopathology. The data on clinical characteristics, pathological subtypes, and imaging features for those patients were analyzed including symptoms, uni- or bilateral eye involvement, single or multiple lesions, tumor location, growth pattern, MRI signal intensity and MRI/CT enhancement patterns. Results: Eyelid swelling (52/82, 63.4%) and proptosis (43/82, 52.4%) were the two most common symptoms for primary orbital lymphomas, whose pathologic subtypes were mainly B-cell lymphomas, especially mucosa-associated lymphoid tissue lymphoma (60/82, 73.2%), and 59 cases (59/82, 72.0%) had unilateral eye involvement. Conjunctiva was the most common location (29/82, 35.4%), followed by eyelid (16/82, 19.5%) and muscle cone (11/82, 13.4%). Of the 66 cases who underwent MRI examinations, 60 showed iso-intensity on T1WI (90.9%), and 51 showed hyper-intensity on T2WI (77.3%). The tumors showed obvious enhancement on contrast-enhanced MRI or CT with 74.2% and 70.5%, respectively. Two other cases showed adjacent bone involvement on CT. Conclusion: B-cell lymphoma, especially mucosa-associated lymphoid tissue lymphoma was the most common primary orbital lymphoma subtype. The tumors mostly had unilateral eye involvement and the conjunctiva was the most common location. The typical imaging features were obvious enhancement on contrast-enhanced MRI or CT that would facilitate tumor diagnosis and treatment decision.