MALT lymphoma
Meaning of MALT lymphoma: A cancer that can sometimes be driven into retreat by treating the infection that provoked it rather than by chemotherapy.
Definition of MALT lymphoma
MALT lymphoma is a slow-growing cancer of B lymphocytes arising in mucosa-associated lymphoid tissue, the patches of immune tissue lying within the linings of the stomach, gut, lung, salivary glands, thyroid and eye. It tends to stay in the organ where it began for a long time. The stomach is much the commonest site, and years of inflammation there usually precede it.
Where does the tissue it grows from come from?
Healthy linings hold little organized immune tissue at birth. It accumulates in response to whatever the surface meets: bacteria, food, inhaled particles, or the body's own tissue under autoimmune attack. Once a patch of lymphoid tissue has formed in the mucosa, its B cells sit in a state of constant stimulation, dividing again and again. Every round of division is a chance for a genetic mistake, and the lymphoma emerges from a cell that has gathered enough of them to keep growing once the original stimulus is gone.
What provokes it?
| Site | Usual trigger |
|---|---|
| Stomach | Long-standing Helicobacter pylori infection |
| Salivary gland | Sjogren syndrome, an autoimmune condition |
| Thyroid | Hashimoto thyroiditis |
| Small bowel | Chronic Campylobacter jejuni infection |
| Surface of the eye | Chlamydia psittaci in some regions |
The stomach form is the one that changed how the disease is understood. In a large share of cases, clearing the bacterium with antibiotics makes the lymphoma itself regress, which puts it among the very few cancers treated in part by treating an infection. Tumors carrying a particular chromosome rearrangement have become independent of the bacterium and do not respond that way.
How does it compare with other lymphomas?
It sits in the B-cell lymphoma group within non-Hodgkin lymphoma, in the indolent or slow-growing half. Its full name is extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, and extranodal means it starts outside the lymph nodes. That behavior sets it apart, since most lymphomas begin in nodes and spread widely while this one often stays local for years. A minority transform over time into an aggressive large cell lymphoma, which behaves and is managed quite differently.
Also known as
Used in a sentence
Endoscopic biopsy confirmed a gastric MALT lymphoma confined to the mucosa.
Good to know
The gastric form is tied to Helicobacter pylori, and eradicating the bacterium alone leads to regression in many cases, although tumors carrying a particular chromosome translocation no longer depend on the infection.