Goyal, ManuDattatreya, Palinki SGoud, IrawathyMurthy, Sudha S2012-09-282012-09-282010-10Goyal Manu, Dattatreya Palinki S, Goud Irawathy, Murthy Sudha S. Cryptic PML-RARα positive acute promyelocytic leukemia with unusual morphology and cytogenetics. Indian Journal of Pathology & Microbiology. 2010 Oct-Dec; 53(4): 817-819.http://imsear.searo.who.int/handle/123456789/141822Acute Promyelocytic Leukemia (APL) is different from other forms of acute myeloid leukemia (AML), to the reason being the potential devastating coagulopathy and the sensitivity to all-trans retinoic acid (ATRA) and arsenic trioxide (As 2 O 3 ). We hereby present a case of APL, morphologically distinct from the hypergranular APL; however, the flow cytometry revealed a characteristic phenotype showing dim CD45, bright CD13, bright CD33 and dim CD117 positivity. These were negative for CD34, HLA-DR, B-lymphoid and T-lymphoid lineage markers. Conventional cytogenetics revealed a distinct karyotype of a male with translocation t(4;15)(q34.2:q26.3). However, interphase florescence-in-situ hybridization (FISH) revealed PML/RARA fusion signal on chromosome 15 in 90% cells. The cryptic translocations may be missed on conventional cytogenetics, however, need to be picked by other techniques as FISH.enAcute promyelocytic leukemiacytogeneticsflow cytometryflorescence-in-situ hybridizationcrypticArticle