Marginal zone lymphomas are a group of low grade Non Hodgkin's lymphoma (NHL) that arise from the marginal zone of B cell germinal follicles in lymph nodes. There are three types of marginal zone lymphomas depending on the site of origin. These include: Mucosa-accosiated lymphoid tissue (MALT) splenic and extranodal marginal lymphoma.
The marginal zone in the germinal follicles undergoes hyperplasia in response to infection or antigens.
MALT lymphomas are the most common type of NHL with an annual incidence of 5-8% The most common sites among MALT lymphomas are the stomach and thyroid. Stomach MALT lymphomas are associated with H.Pylori infection. Extranodal and splenic marginal zone lymphomas are rare and form around 1% of all NHL . There is an increased incidence in patients over the age of 60.
Common symptoms include
- gastro-esophageal reflux
- epigastric pain
- eye redness (in involvement of ocular adnexa)
- unilateral salivary gland enlargement
- colicky abdominal pain (in involvement of intestines)
- cough (in pulmonary involvement)
The most commonly reported genetic abnormalities are t(11,18) and trisomy 3.
On histology, marginal zone hyperplasia and involvement of the interfollicular zone with malignant cells is seen. The malignant cells are of B cell origin.
The imaging findings of marginal zone lymphomas depend on the site or origin at their corresponding stage.
In abdominal involvement, enlargement of the para-aortic, retroperitoneal and mesenteric lymph nodes is often seen. The 'floating aorta' sign may also be seen.
In the chest, mediastinal lymph node enlargement is seen.
Compression of the dural sac by an extradural mass can also be seen.
PET imaging reveals increased FDG uptake in the affected lymph nodes.
Treatment and prognosis
In cases of gastric MALTomas, H. Pylori is often indicated.
Locoregional radiotherapy is often first line for low stage disease.
If chemotherapy is indicated, rituximab, cyclophosphamide, vincristine and prednisolone (R-CVP) are used.