Malt lymphoma

Purpose To review the histomorphology, immunophenotype and genotypic features of conjunctival "MALT" lymphomas. Methods The conjunctival lymphomas represent the malignant end of the spectrum of lymphoproliferative lesions occurring in this site. The new W.H.O. Lymphoma Classification is the most suitable system for subdividing the conjunctival lymphomas, whereby the extranodal marginal zone B‐cell lymphoma of MALT type (or “MALT lymphoma”) represents the most common lymphoma subtype. Results MALT lymphomas are characterized by mainly small B‐cells in the marginal zone. Their immunophenotype is: CD20+, CD43 (+/‐), BCL‐2, IgM+, and a low Ki‐67 growth fraction. A number of chromosomal changes have been described in conjunctival MALT lymphomas, and include trisomy 3, t(14;18), t(3;14), t(11;18), t(1;14) and loss of 6q23.3‐24. Through differing pathways, these chromosomal alterations result in the dysregulation of NF‐KB, and hence the uncontrolled proliferation of lymphocytes. In some geographical regions, there may be an association between these neoplasms and microorganisms, such as Chlamydia, Helicobacter as well as HCV. Management of patients with MALT lymphomas includes a thorough systemic medical examination to establish the clinical stage of the disease. The majority of patients with conjunctival lymphoma have Stage IE disease (Ann Arbor); however, systemic spread is not uncommon. Reported prognostic criteria for MALT lymphomas are few but include stage of disease at presentation; serum lactate dehydrogenase level; and tumour cell growth rate. A new more refined clinical staging system has been proposed by the TNM/AJCC committee and is to be published in its 7th Edition. Conclusion Although the most common lymphoid neoplasm of the conjunctiva, there is still much to learn about MALT lymphomas.