ABSTRACT
Objective@#To investigate the genetic screening methods for cryptic acute promyelocytic leukemia (APL) to further explore its clinical prognosis.@*Methods@#From June 2016 to November 2018, we collected 373 newly diagnosed APL cases. The patients were retrospected by the results of PML-RARα detections both by RT-PCR and i-FISH, those who harbored positive PML-RARα detection by RT-PCR and negative by i-FISH were chosen. Metaphase FISH and Sanger sequencing were further performed to verify these results.@*Results@#A total of 7 cryptic APL cases were discovered. These cases had tiny fragment of RARα inserted into PML in chromosome 15, formed ins (15;17) . The 7 cryptic APL cases had no PML-RARα gene subtype specificity, involving 5 cases in L subtype, 1 case in S subtype and 1 case in V subtype respectively. After the treatment of retinoic acid and arsenic or anthracyclines, 6 cases achieved complete remission, 1 case died of intracranial hemorrhage on the 6th day of therapy.@*Conclusion@#The size and covering position of PML-RARα probe should be taken into account when PML-RARα was performed by FISH on APL patients. Furthermore, combination with Metaphase FISH could improve the recognition of cryptic APL. There were no differences between the cryptic and common APL patients in terms of clinical features and treatment choices. Cryptic APL patients also had a good response to the therapy of retinoic acid and arsenic or anthracyclines.
ABSTRACT
Chronic myelogenous leukaemia (CML) is a myeloproliferative neoplasm that is almost always characterised by the presence of t(9;22)(q34;q11.2). Approximately 5% to 10% of CML patients lack cytogenetic evidence of t(9;22)(q34;q11.2) but have the breakpoint cluster region (BCR)/ABL1 fusion, as revealed by fl uorescence in situ hybridisation (FISH) or the reverse transcription-polymerase chain reaction (RT-PCR). We present a case of Philadelphia-negative CML with a cryptic insertion of BCR at 9q34. A 22-year-old woman incidentally presented with marked leucocytosis and anaemia. Her complete blood count results were as follows: white blood cells, 238.61x10(9)/L; haemoglobin, 9.6 g/dL; platelets, 395x10(9)/L. A peripheral blood smear showed leucocytosis with neutrophilia, basophilia, left-shifted neutrophils, and circulating blasts comprising 2% of the total leucocytes. The bone marrow showed a striking increase in megakaryocytes and granulocytic precursors. The myeloid/erythroid ratio was 7.4:1, and blasts comprised up to 1.8% of all nucleated cells. Bone marrow sections revealed active megakaryopoiesis and granulopoiesis with 100% cellularity. Chromosomal analysis revealed a normal karyotype. However, interphase FISH using a dual-colour BCR/ABL1 fusion probe showed an atypical pattern consisting of one red, two green, and one fusion (1R2G1F) signal in 97.5% of the 200 analysed cells. Metaphase FISH revealed a single BCR/ABL1 fusion signal on chromosome 9. RT-PCR was positive for BCR/ABL1 (b3a2). Quantitative PCR revealed a normalised copy number of 15.32. The patient started her treatment with imatinib, reached a complete molecular response eight months afterwards, and has been coping well without any adverse events.