Using the ALK FISH detection kit, the 3’ and 5’ ends
of the ALK gene are differentially labeled with red or
green fluorescent probes. In benign cells, two fused
signals should be detected. In 60-70% of all of the ALK
rearrangements, the EML4-ALK gene fusion occurs
through only inversion, and therefore narrowly separated
(two to three signals apart) red and green signals are
detected in addition to the normal fusion signal. In the
other 30-40% of the cases, gene fusion occurs through
an interstitial deletion together with an inversion of EML4,
which lead to a single red signal without a corresponding
green signal, in addition to the normal fusion signal