Management of non-Hodgkin lymphomas arising at extranodal sites

Primary extranodal lymphomas are relatively rare non-Hodgkin lymphoma presentations with either no or only "minor" nodal involvement along with a clinically "dominant" extranodal component, to which primary treatment must often be directed. Clinical presentations depend largely on the localization and are similar to those of other malignancies affecting that specific organ. In addition to the histological subtype, the primary organ of origin represents the most significant prognostic factor due to differences in natural history and, mainly, in management strategies related to organ-specific problems. In principle, as for primary nodal disease, treatment strategies depends on the patient's clinical conditions, the extent and/or location of the disease, and the histological type. In general, for stage I and II disease with low tumor burden, local therapy is a relevant option both for cure and local control. In advanced stage disease, systemic chemoimmunotherapy is usually required. Localizations with particularly poor survival are the enteropathy-type T-cell lymphoma, the primary testicular diffuse large B-cell lymphoma, and the primary CNS Lymphoma. However, recent studies have shown that site-tailored treatment strategies in testis and brain lymphoma may result in a significant outcome improvement. Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is the most common indolent subtype. This lymphoma usually arises in mucosal sites where lymphocytes are not normally present and where a lymphoid infiltration is acquired in response to either chronic infectious conditions or autoimmune processes: Helicobacter pylori gastritis, Hashimoto's thyroiditis, Sjögren syndrome. Indeed, a pathogenetic link between gastric MALT lymphoma and H. pylori is strongly suggested by the regression of gastric MALT lymphoma (in approx. 75% of cases) after antibiotic eradication of the microorganism.