Primary Pulmonary MALT Lymphomas Show Frequent and Heterogenous Cytogenetic Abnormalities, Including a Previously Unreported MALT1-IGH Translocation
Reviewer: Tracy d'Entremont, MD
Last Modified: December 8, 2002
Presenter: Ellen D. Remstein
Presenter's Affiliation: Mayo Clinic; Rochester, MN
Type of Session: Scientific
- Mucosa-associated lymphoid tissue (MALT) lymphoma is a low-grade B-cell malignant lymphoma that arises in diverse extranodal sites.
- t(11;18)(q21;q21), which fuses AP12 to MALT1 is specifically associated with MALT lymphoma and is it's most frequent structural chromosomal abnormality
- aneuploidy, particularly trisomy 3,7,12,and 18 is also common in MALT lymphoma
- t(11;18)and aneuploidy occur predominantly in mutually exclusive subsets of MALT lymphomas suggesting different pathogenetic pathways.
- Most cytogenetic analyses of MALT lymphomas have been conducted on gastric tumors
- The range of cytogenetic abnormalities in primary pulmonary MALT lymphoma is unknown.
Materials and Methods
- Flourescence in situ hybridization (FISH) was performed on paraffin embedded tissue from 28 primary pulmonary MALT lymphomas.
- FISH probes for AP12-MALT1 were 2 color probes that spanned both breakpoints, resulting in a dual fusion pattern in positive cases.
- Centromeric probes for chromosomes 3,7,12,and 18 were applied in all cases.
- 7/28 (25%) of primary pulmonary MALT lymphomas demonstrated the AP12-MALT1 fusion protein in a median of 65% of cells.
- Of those AP12-MALT1 positive tumors, aneuploidy was rare, with only 2 cases also demonstrating trisomy 3.
- 11/28 (39%) of cases were aneuploid alone with:
10 cases of trisomy 3
0 cases of trisomy 7
3 cases of trisomy 12
6 cases of trisomy 18
- 3/28 (11%) of cases were + for MALT1-IGH
2 of these 3 cases also had trisomy 3 and 12
the other case had trisomy 11
- Cytogenetic abnormalities are frequent amd more complex in primary pulmonary MALT lymphomas than in those reported from other locations.
- Aneuploidy and t(11;18) are predominantly seen in mutually exclusive groups, supporting the hypothesis that they represent different pathogenetic pathways.
- A new potential pathogenetic pathway in which MALT1 may be activated by the IGH promoter region (MALT1-IGH) has also been identified.
MALT lyphomas are a heterogenous group of tumors. Understanding the genetic abnormalities of these tumors is important in describing the malignant phenotype and may help to uncover new targeted therapies.
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