To report one case of primary intraocular lymphoma confirmed by endoretinal biopsy and clinical experience.

A 65 year-old man complaining of persistent decreased visual acuity was referred to our hospital. Biomicroscopic examination showed bilateral vitreous cells and small round yellowish inflammatory lesions at the level of the retinal pigment epithelial cells. The disc of the left eye was pale in color. Fluorescein angiographic examination of the left eye showed intermingling round hyperfluorescent and hypofluorescent lesions. We performed diagnostic vitrectomy due to unresponsiveness to oral steroid therapy, but the result was negative. We finally performed an endoretinal biopsy, which showed tumor cells with H&E staining and strong immunoreactivities against CD 20 and CD 79a indicating the presence of B cells. We diagnosed this case as primary intraocular lymphoma and performed multiple-cycle chemotherapy with high-dose methotrexate. The ocular signs and symptoms were improved after chemotherapy.

Endoretinal biopsy could be another diagnostic tool for confirming suspected primary intraocular lymphoma in cases showing negative results with diagnostic pars plana vitrectomy and cytology.