The API2/MALT1 DNA-FISH probe is designed to detect the translocation between the API2 gene located at 11q21 and the MALT1 gene located at 18q21 using fluorescence in situ hybridization (FISH).^[1]  The translocation between the API2 and MALT1 gene, designated as t(11;18)(q21;q21), can be detected in around 15% of mucosa-associated lymphoid tissue (MALT) lymphomas, but varies in frequency based on primary tumor site.^[2]  In pulmonal and gastric MALT, t(11;18) is found more frequently (38-53% and 22-24%, respectively) and in these cases is almost always the only detected chromosomal abnormality.^[2]  When observed in gastric MALT lymphoma, t(11;18) is highly associated with a lack of response to antibiotic H pylori eradication treatment.^[3,4]