To report a rare case of orbital malignant lymphoma that occurred in a patient with acquired immunodeficiency syndrome.

A 39-year-old male with acquired immunodeficiency syndrome complained of proptosis and loss of visual acuity. The best corrected visual acuity of his right eye was no light perception, and the BCVA of his left eye was 1.0. Ocular movement was limited, and esotropia of 15 prism diopters was detected. Exophthalmometry measurements showed a significant difference between both eyes (right eye was 18 mm, left eye was 15 mm). Computed tomography scans of the patient's orbit with contrast showed an enhancing mass in the right orbit, so a biopsy was performed. A biopsy specimen of the mass revealed non-Hodgkin's lymphoma (anaplastic variant, diffuse large B cell type). Distant metastasis was not found using abdominal and thoracic computed tomography and positron emission tomography. He underwent radiotherapy (30 Gy, 15 times).

Orbital non-Hodgkin's lymphoma (B cell type) in a patient with AIDS is rare, but our case showed a good response to radiation therapy.