The non-Hodgkin lymphoma subtype of marginal zone lymphoma represents a group of lymphomas that have been historically classified together because they appear to arise from post-germinal center marginal zone B cells and share a similar immunophenotype: positive for B cell markers CD19, CD20, and CD22, and negative for CD5, CD10, and usually CD23.
Several marginal zone lymphoma subtypes are recognized in the World Health Organization classification of lymphoid neoplasms:
Extranodal marginal zone lymphoma of mucosa associated lymphoid tissue (MALT lymphoma)
Primary cutaneous marginal zone lymphoma
Nodal marginal zone lymphoma
Splenic marginal zone lymphoma
Arises in :
Stomach
Salivary gland
Lung
Small bowel
Thyroid
Ocular
Adnexa
Skin
Elsewhere.
MALT lymphoma
Definition
B-cell lymphoma involving the mucosa-associated lymphoid tissue (MALT), frequently of the stomach, but may occur in any mucosal site
Incidence
5% of all lymphoma and almost 40% of all gastric lymphoma
Classification
Should be classified according to TNM classification, rather than Ann Arbor system
Aetiology
Chronic inflammation
H. pylori
Clinical
MALT can be in: stomach, eyes, thyroid, salivary glands, other GI sites
can disseminate to other mucosal associated lymphoid tissue (MALT) sites, LN, or BM in about 30% of cases
disseminated disease in 34% at diagnosis
B symptoms uncommon
Pathology
Stomach normally lacks lymphoid tissue but develops mucosa associated lymphoid tissue in response to H.pylori infection
In gastric tumours: T-cells are driven by H. pylori antigens → stimulate B cells → lymphoma
Usually indolent tumors
Investigations
Gastroscopy + Bx
CT
EUS – to determine the depth of invasion of the tumour, for optimum treatment
Therapy directed at the antigen (H pylori) results in regression of most (≈70-80%) early (T1) lesions
non-bulky flat mucosal lesions and localized disease without lymph node spread or distant metastases
Pts with high-grade lymphomas & MALTs that involve the muscularis, or ≥ T2 or LN +ve are unlikely to respond to eradication therapy alone these pts should be referred to oncology for Rx according to standard lymphoma protocols
But there has been reports of some pts with primary high-grade B-cell gastric lymphoma (ie DLBCL) who attained complete remission following antibiotic Rx
Non-responsive tumours → surgery (gastrectomy) / radiation ± chemo
Prognosis / Natural Hx
high complete remission rates & potentially long survival, up to 80% at ≥10 years
Follow-up
EUS can be used to re-stage pts after anti-H.pylori therapy or after chemo
Pts who have residual gastric wall thickening inevitably have residual lymphoma (even if Biopsy -ve) (ANZ 07; 77:166)>)