Unravelling the mysteries of ocular lymphomas

Purpose There has been a bewildering evolution in the nomenclature of lymphomas, including ocular lymphomas. Confusing as this may seem, this is a reflection of impressive advances in our understanding of lymphoma pathogenesis, mainly as a result of immunohistology and molecular biological research. This overview will summarise the main successes of ocular lymphoma research and its translation into clinical practice. Methods The WHO lymphoma classification is based on the morphology, immunophenotype and genotype of tumour cells and their relationship to a putative cell of origin. Most ocular adnexal lymphomas (OAL) are low‐grade B‐cell lymphomas (EMZL), thought to arise from marginal zones of lymphoid follicles. Their development is associated with chromosomal abnormalities, autoimmune disease & microorganisms. Traditionally, OAL have clinically been staged using the Ann Arbor system, which has many shortcomings. The novel TNM‐based staging system defines disease extent more precisely and allows for analysis of site‐specific factors. Results Retinal lymphoma has been vaguely subsumed under the term "primary intraocular lymphoma": it is a high‐grade B‐cell malignancy, associated with a poor prognosis as a result of CNS disease. Immunophenotyping and genetic analysis suggest that retinal lymphomas arise from early post‐germinal centre cells. Other less common intraocular lymphomas include primary choroidal lymphomas (a low‐grade EMZL), primary iridal and ciliary body lymphomas, and secondary uveal lymphomas. Conclusion Ocular lymphomas are heterogenous tumours with differing subtypes and varying clinical courses. Precise nomenclature together with exact subtyping and clinical staging is essential, to understand ocular lymphoma histiogenesis and to facilitate studies improving prognostication and therapy.