Cytogenetic Abnormalities in Gastric MALT Lymphoma
The most characteristic cytogenetic abnormality in gastric MALT lymphoma is t(11;18)(q21;q21) resulting in the BIRC3-MALT1 fusion, though multiple other translocations and trisomies are also recognized. 1
Primary Chromosomal Translocations
The European guidelines and ACMG technical standards identify several recurrent translocations specific to extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma):
Most Common Translocation
- t(11;18)(q21;q21); BIRC3-MALT1 is the most frequent translocation, occurring in approximately 21-25% of gastric MALT lymphomas 1, 2, 3, 4
- This translocation is highly specific for MALT lymphoma and strongly predicts resistance to Helicobacter pylori eradication therapy 1, 2, 3, 4
- Detection is clinically useful for identifying patients unlikely to respond to antibiotic therapy 1
Other Immunoglobulin-Related Translocations
- t(1;14)(p22;q32); BCL10-IGH - rare in gastric MALT lymphoma 1, 2
- t(14;18)(q32;q21); MALT1-IGH - also rare, and cytogenetically identical to the BCL2-IGH translocation seen in follicular lymphoma, requiring FISH for differentiation 1
- t(3;14)(p14.1;q32); FOXP1-IGH - occurs in approximately 6% of cases 1, 2
Numerical Chromosomal Abnormalities
Trisomies
Gastric MALT lymphomas frequently exhibit numerical chromosomal gains:
- Trisomy 3 - present in approximately 44-46% of cases, making it the most common numerical abnormality 1, 5, 6
- Trisomy 18 - detected in approximately 19-21% of cases 1, 5
- Trisomy 12 - found in approximately 12-28% of cases 1, 5, 6
- Gain of chromosome X - unexpectedly high frequency of 36% in gastric MALT lymphomas 5
Clinical Significance of Numerical Abnormalities
- Extra copies of MALT1 (often indicating partial or complete trisomy 18) occur in approximately 25% of cases and are significantly associated with progression or relapse, representing an independent adverse prognostic factor for event-free survival 2
- Trisomy 3 may be present in preneoplastic lesions, suggesting early involvement in lymphomagenesis 6
Diagnostic Testing Recommendations
FISH Analysis
- Fluorescence in situ hybridization (FISH) studies for detection of t(11;18)(q21;q21) may be useful for identifying patients unlikely to respond to antibiotic therapy 1
- FISH is required to distinguish between t(14;18); MALT1-IGH and t(14;18); BCL2-IGH translocations in cases with differential diagnosis 1
Important Caveats
- Genetic testing is not generally performed routinely for all lymphoma cases and is usually restricted to cases with differential diagnosis or for prognostication purposes 1
- Results must be integrated with histological reports, immunophenotype, and other genetic abnormalities, as many abnormalities are not specific to a particular disease 1
- The presence of t(11;18) is associated with H. pylori-negativity, resistance to H. pylori eradication, and Bcl10 nuclear expression 2, 4