MALT gastric lymphoma
Gastric MALT lymphoma
Marginal zone lymphomas of the MALT type are B-cell neoplasms involving extranodal tissues and lazy clinical behavior. The stomach is the most common site, and Helicobacter pylori infect most patients. An increase in the resistance of this bacterium to several antibiotics has been observed in the last years, and this fact has determined the review of treatment guidelines. In areas with resistance to clarithromycin greater than 15%, classical triple therapy should be abandoned, and quadruple regimens with or without bismuth are currently recommended. Thus, these new guidelines for eradication should be applied to patients with gastric MALT lymphoma associated with H. pylori infection.
WHAT IS GASTRIC MALT LYMPHOMA?
MALT lymphoma is a type of lymphoma that can affect various human body organs, including the stomach (gastric MALT lymphoma). The term “MALT” is the acronym for “mucosa-associated lymphoid tissue.” Lymphomas can be made up of two types of cells (lymphocytes): type B (including MALT lymphoma) and type T. In general, type B lymphomas are more benign than type T; in fact, MALT lymphomas are generally low-grade (mild), although, exceptionally, they can progress to higher-grade (more malignant) lymphomas.
WHAT IS ITS FREQUENCY?
The most common stomach tumor is adenocarcinoma (95% of cases), with lymphoma second in frequency (representing approximately 5% of gastric tumors). Among gastric lymphomas, the MALT-type is, in turn, the most common.
HOW IS IT PRODUCED?
Most (about 90%) of MALT lymphomas appear in people infected with a bacterium that colonizes the stomach called Helicobacter pylori (H. pylori for short). This bacterium is responsible for the appearance of gastritis of a particular type, with abundant lymphoid follicles. These lesions are a prerequisite for the later development of MALT lymphoma, in which malignant cells (lymphocytes) end up infiltrating the glands of the stomach.
HOW IS IT CLASSIFIED ACCORDING TO ITS EXTENSION?
The most widely used classification is that of Ann Arbor (modified by Musshoff), which subdivides MALT lymphoma into the following stages: I (only affects the stomach, respecting the lymph nodes, and in turn is subdivided into I1 – limited to mucosa and submucosa, which are the most superficial layers of the gut- and I2 -when it invades the deeper layers of the stomach-); II (if it affects the lymph nodes on the same side of the diaphragm as the stomach); III (if it affects the lymph nodes on both sides of the diaphragm); and IV (when the lymphoma is spread throughout the body).
WHAT CLINICAL MANIFESTATIONS DOES IT HAVE?
The clinical manifestations are usually nonspecific (dyspepsia, nausea, and vomiting, anorexia, weight loss, etc.) and are similar to those of many other digestive diseases, such as a peptic ulcer or different types of gastric tumors. Occasionally, complications can occur, such as digestive bleeding or, much more rarely, a gastric perforation.
HOW IS IT DIAGNOSED?
Endoscopy (gastroscopy) is the fundamental diagnostic technique; through it, a series of suggestive lesions of MALT lymphoma can be visualized.
The diagnosis will be confirmed by a histological study (assessment through the microscope by the pathologist) of the biopsies obtained during gastroscopy. Tumor cells frequently adopt a patchy distribution in the gastric cavity. On the other hand, it is advisable also to use special techniques (immunohistochemical or molecular) to differentiate with certainty between true MALT lymphoma and a proliferation (growth) of a purely inflammatory type.
It is essential to confirm an associated H. pylori infection (by a breath test, stomach biopsy, or blood sample).
HOW IS YOUR EXTENSION VALUED?
For the extension study, before the administration of the treatment, the following are required:
- Exhaustive physical examination
- General laboratory tests (including various determinations)
- Chest x-ray
- Computed tomography of the chest and abdomen
- Bone marrow biopsy
In addition, an endoscopic ultrasound should be performed (using a particular type of endoscope, which has a device attached to the tip that allows an ultrasound of the gastric wall to be executed); This test allows to assess in detail if there is an invasion of the layers of the stomach or involvement of the lymph nodes.
HOW IS IT TREATED?
Curing H. pylori infection is currently the treatment of choice for most gastric MALT lymphomas. To do this, an antisecretory agent (omeprazole or similar) is administered along with two or three antibiotics for 10-14 days. The cure of this infection is followed by the remission of the tumor (that is, its disappearance) in the majority (approximately 80%) of the cases. However, this beneficial effect may take a year or even longer appear. Fortunately, tumor remission after H. pylori eradication remains stable over time in most cases. Therefore, the prognosis is generally quite good.
Antibiotic treatment against H. pylori is sufficient in low-grade and early-stage MALT lymphomas, which are the majority, while in the rest of MALT lymphomas
Gastric (high grade or in more advanced stages) eradicating this infection constitutes only part of the treatment, and other complementary therapies must be used (such as chemotherapy, radiotherapy, or, more rarely, surgery).
WHAT ARE CONTROLS NECESSARY AFTER TREATMENT?
Not all low-grade MALT lymphomas respond to H. pylori eradication. Therefore, verification of tumor regression after eradication is mandatory, and periodic endoscopic reviews search for residual lesions. If the cure of the tumor is not confirmed (both endoscopically and histologically) after one year, cancer treatment (chemotherapy or radiotherapy) or surgery should be considered. Some authors believe that it is no longer necessary to perform more control gastroscopies (and that an annual breath test would be enough). Still, most recommend endoscopic controls (for example, annual) for life.