Peter Isaacson Wins INCTR Pathology Award
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Since 2013, INCTR has given an annual award to a pathologist who has made outstanding contributions to pathology. This year, Prof Peter Isaacson FRS, who discovered, with Dennis Wright, MALT (mucosal associated lymphoid tissue) lymphoma was the awardee. Prof Isaacson was born in South Africa and spent much of his professional life as a histopathologist at University College Hospital in London. He made a number of important discoveries as a result of which he was invited to become a Fellow of the Royal Society. Prof Isaacson described MALT lymphomas in 1984. MALT lymphomas occur particularly in the stomach, although any mucosal site may be involved. They fall within the category of marginal zone B cell lymphomas and are of particular interest because they appear to be the consequence of inflammation caused by a bacterium, Helicobacter pylori - the stomach normally lacks lymphoid tissue. When confined to the stomach, MALT lymphomas can be cured with antibiotics alone in the majority of cases. Radiation or surgery may also be curative in patients with localized disease. If tumors are no longer localized, chemotherapy may be effective, but is unlikely to be curative.

Prof Isaacson also described similar lymphomas associated with Hashimoto's thyroiditis and showed that the antibodies made by MALT lymphoma cells are often directed against self-antigens, implicating auto-immune reactivity in the pathogenesis of some lymphomas. A t(11;18)(p21;Q21) chromosomal translocation is present in many MALT lymphomas, giving rise to a fusion gene known as API2-MLT, which is believed to activate the NFkappaB signalling pathway and is predictive of a poor response to therapy. Other translocations involvig the IgG locus at chromosome 14q32 have been described in place of the t(11;18) translocation, namely, t(1;14)(p22;q32) and t(14;18)(p22;q32), which are also believed to activate the NFkappaB pathway. Marginal zone lymphomas also occur in the spleen (splenic marginal zone lymphoma, or SMZL), in the skin, in the ocular adnexae or in lymph nodes. Interestingly, each is associated in a fraction of cases with a different infectious agent: SMZL and nodal marginal zone lymphomas may be associated with hepatitis C virus infection, ocular adnexal tumours (once known as pseudolymphomas) with Chlamydia psittaci and skin marginal zone lymphomas with Borrelia burgdorferi.

Dr Isaacson also recognized the existence of enteropathy-associated T cell lymphoma.

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