Molecular pathology of intraocular lymphomas

Abstract

This article describes recent advances in the understanding of the molecular genetics of intraocular lymphomas. These comprise vitreoretinal lymphoma, primary choroidal lymphoma, primary iris lymphoma and secondary choroidal lymphomas. Following WHO principles, their classification is now based on morphological, immunophenotypical and genotypical features. Retinal lymphoma is a high-grade lymphoma, usually of B-cell type, and is associated with a poor prognosis because of CNS involvement. Immunophenotyping and somatic mutation analysis suggest derivation from early postgerminal center B cells. Chromosomal translocation data suggest that some arise from germinal center B cells, which may have a better prognosis. Primary choroidal lymphoma is a low-grade B-cell lymphoma similar to nonocular, extranodal marginal zone B-cell lymphomas (EMZL). The putative cell of origin is a postgerminal center (memory) B cell. Primary iridal lymphomas are rare, with an equal distribution of B- and T-cell types and with a variable clinical course, most patients succumbing to systemic dissemination. Only one case of primary ciliary body lymphoma has been reported. Secondary choroidal lymphomas/leukemias tend to represent advanced systemic disease. Progress has been made in understanding the histiogenesis of intraocular lymphoma. Further investigations, such as gene expression profiling, are required to identify oncogenic pathways, to enhance prognostication and improve therapy.