ALK and neoplasm: Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase, and in a subset of IMT cases, rearrangements of the ALK gene – located on chromosome 2p23 – have been detected using fluorescence in situ hybridization (FISH) or polymerase chain reaction (PCR).[6] ALK positivity serves as a specific biomarker for distinguishing IMT from other neoplasms; however, ALK negativity does not preclude the diagnosis.