Marginal zone lymphoma is a type of low grade B-cell non-Hodgkin lymphoma. It can be sub-classified as nodal, splenic, and extra-nodal (EMZL) of mucosa-associated lymphoid tissue (MALT). They make up 5-15% of all non-Hodgkin lymphomas in the Western world.
EMZL account for around 2/3 of MZL. The commonest site is the stomach (where there is a strong association with Helicobacter pylori infection), followed by eyes and associated tissues, lungs, and salivary glands.
Tissue biopsy is essential for diagnosis, and immunohistochemistry must show CD20 positivity. The diagnosis is further supported by histological appearances and IHC negativity for markers of other lymphomas, including CD5, CD10, MYD88, cyclin D1. Staining for H. pylori is essential in order to guide treatment – if negative, other diagnostic means should be pursued e.g. serology, urea breath test, stool antigen test.
Additional investigations are recommended such as full blood count, hepatic/renal function tests, LDH, beta-2 microglobulin, serum protein electrophoresis and immunofixation, hepatitis/HIV testing. Bone marrow biopsy is recommended but its use varies. The ideal modality for staging is not universally agreed, and both CT or PET-CT are used. For gastric EMZL, oesophagogastrodudodenoscopy (OGD) is essential in order to collect biopsies from multiple sites (the disease is often multifocal). Endoscopic ultrasound may be of use to examine for perigastric lymphadenopathy, although often imaging will suffice.
Treatment involves H. pylori eradication triple therapy with a proton pump inhibitor for 4 weeks and 2 antibiotics for 10-14 days – regardless of H. pylori status. Urea breath test or stool antigen test should be checked 6 weeks after commencing treatment – if still positive, an alternative eradication regime should be sought. In positive cases, this therapy will result in remission in 75%.
Follow up should be by OGD and biopsy every 3-6 months for a minimum of 2 years. If evidence of residual or recurrent lymphoma, watchful waiting is advised unless the patient is showing symptoms or signs of disease progression. In these cases, radiotherapy can be considered for localised disease. Otherwise chemo-immunotherapy is indicated – agents vary but involve rituximab either as single agent or in combination with another agent such as chlorambucil, bendamustine, and lenalidomide.
Marginal zone lymphomas: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. https://www.annalsofoncology.org/article/S0923-7534(19)35465-1/fulltext