Ocular Adnexal Lymphoma Ocular adnexa lymphomas (OAL) represent 8% of all extranodal non-Hodgkin lymphomas (NHL), which develop as primary or secondary tumour manifestations in the orbit, conjunctiva, eyelids, and lacrimal glands and drainage system. OAL are sub-typed according to the World Health Organisation Classification, with extranodal marginal zone B-cell lymphoma of the ocular adnexa (EMZL-OA) accounting for 60-70% of these tumours. The remaining 30-40% of OALs comprise diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), plasmacytoma, mantle cell lymphoma (MCL) and T-cell lymphomas, in decreasing frequency. The incidence of EMZL-OA has inexplicably increased over the last two decades at a rate of 6% annually.
Although most EMZL-OA patients present initially with limited disease, up to 1/3 subsequently develop disseminated lymphoma. Currently it is difficult to predict disease course both clinically and histopathologically, although various parameters, such as anatomical location, serum lactate dehydrogenase levels, patient age and gender as well as tumour cell Ki-67 growth fraction have been suggested to be of prognostic value.
The pathogenesis of OAL is currently poorly understood. Previous studies have suggested infection with Chlamydia could contribute to the development of OAL in some countries, however this remains controversial. Recently, deletion of 6q23.3-24.1 with loss of A20, a putative tumour suppressor gene and a negative regulator of the NF-kB signalling pathway, has been described as a predictive biomarker for EMZL-OA recurrence and systemic dissemination. Promoter hypermethylation and inactivating mutations of A20 are reported to exist in about one third of EMZL-OA cases.
Although most EMZL-OA patients present initially with limited disease, up to 1/3 subsequently develop disseminated lymphoma. Currently it is difficult to predict disease course both clinically and histopathologically, although various parameters, such as anatomical location, serum lactate dehydrogenase levels, patient age and gender as well as tumour cell Ki-67 growth fraction have been suggested to be of prognostic value.
The pathogenesis of OAL is currently poorly understood. Previous studies have suggested infection with Chlamydia could contribute to the development of OAL in some countries, however this remains controversial. Recently, deletion of 6q23.3-24.1 with loss of A20, a putative tumour suppressor gene and a negative regulator of the NF-kB signalling pathway, has been described as a predictive biomarker for EMZL-OA recurrence and systemic dissemination. Promoter hypermethylation and inactivating mutations of A20 are reported to exist in about one third of EMZL-OA cases.
