Test Code

F MALT; FP MALT

Test Synonyms

18q21, t(11;18)(q21;q21), MALT lymphoma-associated translocation 1 gene

Associations

Mucosa-associated lymphoid tissue (MALT lymphoma)

Methodology

Fluorescence in situ Hybridization (FISH)

Turnaround Time

3-5 days

Specimen Requirements

F MALT
5mL peripheral blood in sodium heparin
3mL bone marrow in sodium heparin
Fixed cytogenetically prepared cells in sterile centrifuge tube with pellet visible in 3:1, Methanol:Acetic Acid

FP MALT
FFPE tissue is acceptable for FISH analysis. Preferred fixative is 10% neutral buffered formalin. Tissues preserved in B5 fixative or decalcified are usually not suitable for FISH. Tumor sections cut 3-5 µm thick and mounted on positively charged organosilane coated (silanized) slides work well. Request several unstained sections (two for each probe) and one H&E stained slide

Specimen Stability

Storage & Handling

4°C to 25°C during transit, but specimens may be transported on refrigerated gel packs. Do not allow the gel pack to come in contact with the specimen. Do not freeze. Extreme temperatures should be avoided.

Causes for Rejection

Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells; Improper fixative

Reference Range

A normal cell will show two fusion (yellow or orange/green fused) signals representing two intact copies of 18q21. A cell with a rearrangement involving the MALT1 gene will show a fusion signal on the normal chromosome 18 along with one orange and one green signal indicating disruption of the MALT1 gene on the rearranged chromosome.

Description

Translocation (11;18)(q21;q21) has been associated with extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). Translocation (11;18) leads to the fusion of the apoptosis inhibitor-2 (API2) gene and the MALT lymphoma-associated translocation (MALT1) gene. However, it has been found that 18% of MALT lymphomas have t(14;18)(q32;q21) or a translocation involving the IGH and MALT1 gene. MALT lymphomas with t(11;18)(q21;q21) usually do not have additional genetic aberrations, which is in contrast to t(14;18)(q32;q21) cases. Aneuploidy is most often seen in the majority of t(14;18)(q32;q21) MALT lymphomas.  >br>
FISH can detect this rearrangement in either interphase or metaphase cells.

References

1. Bertoni F et al. (2006). Delving deeper into MALT lymphoma biology. J Clin Invest. 116(1):22.
2. Streubel B et al. (2003). t(14;18)(q32;q21) involving IGH and MALT1 is a frequent chromosomal aberration in MALT lymphoma. Blood. 101(6):2335.
3. Cook JR. (2003). T(14;18)(q32;q21) involving MALT1 and IGH genes in an extranodal diffuse large B-cell lymphoma. Hum Pathol. 34(11):1212.
4. Cavalli F et al. (2001). MALT lymphomas. Hematology.(1):241.