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)
2.0 mL (min. 1.0 mL) peripheral blood in sodium heparin preferred, EDTA accepted
1.0 mL (min. 0.5 mL) bone marrow in sodium heparin preferred, EDTA accepted
5 mm^3 fresh tissue or 3.0 mL (min. 2.0 mL) FNA in MPLN RPMI media
Whole blood and bone marrow, ship ambient
Fresh tissue and FNA ship in a Styrofoam container with a cool/refrigerated pack (Do not allow cool pack to directly contact sample)
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.