RT-PCR analysis demonstrating the presence of theNPM-ALKfusion transcript and the absence of mRNA for the extracellular portion of ALK in 2 cases of ALK-positive B-cell lymphoma. RT-PCR was performed on total RNA extracted from the patient tissue samples, a known positive control, and a known negative control. The presence of amplifiable RNA was confirmed by RT-PCR amplification of a 321-bp portion of the ubiquitously expressed NPM gene. The analysis demonstrates the presence of 429-bp NPM-ALK and 121-bp 3′ALK (encoding for the intracellular portion of ALK, also present in the NPM-ALK) transcripts and is negative for the 552-bp 5′ALK transcript (encoding for the extracellular portion of ALK).