Primary intraocular lymphoma

Primary intraocular lymphoma (PIOL) is a rare extranodal Non-Hodgkin lymphoma (NHL), involving the retina, the subretinal space, vitreous body and/or optic nerve. The majority of PIOL are diffuse large cell B-cell lymphomas according to the new W.H.O. lymphoma classification with an immunophenotype suggesting an origin from germinal centre cells. PIOL occurs independently or together with primary central nervous system lymphoma (PCNSL), and often presents in the form of a steroid-resistant uveitis. PIOL is one of the most challenging intraocular tumours to diagnose. Cytological examination of vitreal aspirates remains the gold standard for exclusion of neoplastic disease in patients with idiopathic uveitis. Various techniques, particularly the polymerase chain reaction analysing clonal rearrangements of the immunoglobin heavy chain or the T-cell receptor genes, prove to be useful adjuncts. Chorioretinal biopsies increase the chances of diagnosing or excluding a PIOL involving the retina and choroid. Furthermore, they allow exact subtyping of the malignant lymphoma when present, enabling exclusion of an ocular manifestation of a systemic lymphoma. Currently, most PIOL/PCNSL are treated with systemic chemotherapy. Ocular recurrences are often treated with radiotherapy, and increasingly with intraocular methotrexate. Although the prognosis of patients with PCNS/PIOL remains poor, newer methods enabling earlier diagnosis establishment and treatment are gradually increasing overall survival.