F API MALT*
t(11;18)(q22;q21), MALT lymphoma, Mucosa associated lymphoid tissue translocation gene 1
MALT lymphoma, Non-Hodgkin (NHL), Extranodal marginal zone B-cell lymphoma
Fluorescence in situ Hybridization (FISH)
*Performed by affiliate laboratory
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
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.
Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells; Improper fixative
FISH results indicate whether rearrangement is present or absent.
In a normal cell without the t(11;18), two orange and two green signals will be detected, indicating the presence of two intact copies of chromosome 11 and two intact copies of chromosome 18. In an abnormal cell, two fusion signals representing the two rearranged chromosomes will be observed along with one orange signal and one green signal.
MALT lymphomas (also known as extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue) constitute about 8% of all non-Hodgkin lymphomas. The most common structural abnormality associated with MALT lymphomas is the translocation between 18q21 and 11q22. This rearrangement leads to the fusion of the apoptosis inhibitor-2 (API2) gene and MALT lymphoma-associated translocation (MALT1) gene. In general, MALT lymphomas are low-grade lymphomas regardless of the fact there is often dissemination to other mucosal sites, bone marrow or multiple lymph nodes. Rare cases show histological transformation to aggressive diffuse large-dell lymphoma.
The translocation between 11q22 and 18q21 juxtaposes the 5’API2 gene to the 3’MLT1 gene for a fusion gene that encodes an abnormal, but functioning chimeric protein.
The API2/MALT1 probe assay can be performed on interphase or metaphase cells.