FISH: RARA (17q21) VARIANT TRANSLOCATION

ACUTE PROMYELOCYTIC LEUKEMIA (APL) IN ITS TYPICAL PRESENTATION EXPRESSES PML-RARA AS SEEN IN 95% OF PATIENTS. THESE PATIENTS HAVE GOOD CLINICAL OUTCOME. HOWEVER, 16 ADDITIONAL RARA REARRANGEMENTS HAVE BEEN IDENTIFIED SUCH AS PLZF-RARA, GTF2I-RARA, NUMA-RARA, STAT5B-RARA ETC. THESE CASES OF VARIANT APL HAVE POOR PROGNOSIS AS COMPARED TO TYPICAL APL AS THEIR REPONSE TO TYPICAL THERAPY INCLUDING ATRA & ATO IS NOT GOOD. THIS TEST IS USEFUL FOR VERIFYING RARA STATUS WHEN MORPHOLOGY IS SUSPICIOUS FOR APL BUT T(15;17) FISH TEST IS NEGATIVE. THE TEST HELPS IN EARLY IDENTIFICATION OF THIS GROUP OF PATIENTS SO THAT THEY CAN SWITCH FROM ATRA TO STANDARD CHEMOTHERAPY.