De nove Philadelphia chromosome-positive myelodysplastic syndromes with complex karyotype and p230 BCR::ABL fusion transcript: a case report with a literature review

ABSTRACT Myelodysplastic syndromes (MDS) refer to a set of clonal hematopoietic disorders with fusion transcript as disease progression. Breakpoint cluster region/abelson (BCR::ABL) fusion mostly occurs during the progressive phase from MDS to higher stages and acute leukemia transformation. Besides, it is extremely rare reported on the diagnosis of MDS. Here, the first case of transformation of de nove philadelphia (Ph)-positive MDS to chronic myeloid leukemia (CML) with rapid progression to acute myeloid leukemia (AML) was reported. Fluorescence in situ hybridization (FISH) analysis revealed an atypical BCR::ABL positive signal (2R2G1Y) that accounted for 3% at the diagnosis of MDS and increased to 21.4% at information to CML. The result of multiplex reverse transcriptase polymerase chain reaction (RT–PCR) indicated a rearrangement of e19a2 (p230 BCR::ABL). The treatment with 400 mg of imatinib daily at the transformation from MDS to CML led to a hematological response. However, the patient stopped taking imatinib due to the worsening of cytopenias after five weeks of therapy and rapid progression to AML in another two months. The treatment with azacitidine (AZA) and venetoclax (VEN) achieved partial remission (PR). Unfortunately, the patient relapsed six months after PR and died shortly thereafter. In addition, another 16 cases of adult cases that reported MDS with de nove Ph-positive were also reviewed to learn about clinical features and outcomes.

BCR::ABL positive in myeloproliferative neoplasms is a diagnostic biomarker of chronic myeloid leukemia (CML).Nevertheless, this translocation can also be observed in acute lymphoblastic leukemia (ALL) [6] and acute leukemia of ambiguous lineage (ALAL) [7].The classification of hematopoietic and lymphoid malignancies by the World Health Organization (WHO) (2016 version) added a rare provisional category of acute myeloid leukemia (AML) with BCR::ABL which was revised in 2022 as a new entity that could benefit from tyrosine-kinase inhibitor (TKI) therapy [1,8] Besides, BCR::ABL fusion mostly occurs during the progressive phase from MDS to higher stages and during AL transformation [9].Since it is extremely rare reported on the diagnosis of MDS (de nove Ph-positive MDS), its significance for prognosis and disease management has not been investigated yet.
Here, the first case of transformation of de nove Phpositive MDS to CML with rapid progression to AML was reported.AML was then successfully treated with azacitidine (AZA) and venetoclax (VEN).A brief literature review of adult de nove Ph-positive MDS was also conducted.

Case report
In September 2020, a 76-years-old male presented with pancytopenia for more than one year: white blood cell (WBC) count 1.70 × 10 9 /l, hemoglobin 98 g/l and platelet count 61 × 10 9 /l.No petechiae, hepatosplenomegaly or lymphadenectasis could be found.The bone marrow (BM) smear hyperplsia was obviously active with a myeloid: erythroid ratio of 0.67:1 without ringed sideroblasts.Multilineage dysplasia (MLD) was observed.It included 41% of dysplastic myeloid cells with hypogranular cytoplasm and abnormal chromatin clumping, 18% of dysplastic erythroid cells with megaloblastic changes and multinuclearity, and a normal number of megakaryocytes with small-size micromegakaryas occasionally (Figure 1A).
In January 2022, BM reexamination showed an increase of 6.4% in hypercellularity with blasts.The flow cytometry (FCM) of BM specimens demonstrated that blasts occupied 7.9%, which were positive for CD34, CD117, and HLA-DR, and weakly positive for CD13, CD33 and CD45.However, FISH and RT-PCR revealed that the positive rate of BCR::ABL decreased to 10.6% and 1.04%.The patient agreed to receive chemotherapy with AZA 100 and 133 mg respectively when progressing to the CML-acceleration phase as the PB smear showed 13% blasts in another three weeks.In March 2022, leukocytosis (WBC 13.3 × 10 9 /l) and morphological analysis of BM showed hypercellularity with 28.8% blasts, which was consistent with progression to AML (Figure 1C).However, FISH and RT-PCR showed that the positive rate of BCR::ABL was 9% and 0.569%, respectively.After one course of treatment with AZA 133 mg combined with VEN 400 mg, BM morphology exhibited hypercellularity with 5.6% blasts.The minimal residual disease (MRD) was 1% and 1.45% by FCM and RT-PCR.CC showed 46,XY,t (9;22)(q34;q11) [2]/46,XY [18].After the fifth month of AZA + VEN treatment, MRD was less than 1% by FCM and 3.66% by RT-PCR, and BM smear was hypocellular with 7.6% blasts.It was unfortunate that the patient relapsed in September 2022 and died shortly thereafter.
In the literature review, 38 cases of MDS were reported with Ph-positive.In addition, 18/38 (47.4%) of these cases acquired secondary Ph during transformation to higher stage/leukemias.Four cases of de nove Ph-positive MDSs were excluded: an infant of MDS [11] and three cases of MDS-refractory anemia with excess blasts (RAEBt), which were AML according to the new WHO classification [12][13][14] This case, together with other 16 adult cases with de nove Ph-positive MDS in literature, was enrolled in this study.A total of 17 cases included 10 males and seven females with a median age of 67 , as summarized in Table 1.Median WBC, hemoglobin and platelets were 4.2 (1.7-15.7)× 10 9 /l, 82 (42-125) g/l and 98 (10-325) × 10 9 /l, respectively.

Discussion
Approximately a third of MDS will transform into AL.As is known, prognosis and therapy selection are strongly correlated with cytogenetics.Ph/t(9;22) and its derivative BCR::ABL fusion protein are hallmarks of CML.Nonetheless, this translocation has also been found in ALL, ALAL and AML [1,[6][7][8].The significance of Phpositive MDS remains unclear since few cases of de nove Ph-positive MDS or secondary Ph acquired have been reported in the literature [28][29][30] The median positive rate of Ph at initial diagnosis was 20% (0.243-98.7%) in the case series of de nove Ph-positive MDS (Table 1), but close to 100% in CML.Moreover, 6/ 17 (35.3%)cases were Ph-positive with CK; 3/17 (17.6%) cases were cryptic BCR::ABL-positive with CK; 5/17 (29.4%) cases were Ph-positive without additional CAs; the remaining 3/17 (17.7%) cases were Ph-positive with other CAs, such as 5q-, −4 and +8.Furthermore, 10/13(76.9%)cases transformed to AL or higher stage except for four cases with early death (within one month).The median time of progression and overall survival (OS) was 13 (4-51) and 11 (0.25-52) months, respectively.The eventual death rate was 82.4% (14/ 17).An overall analysis of these data showed a poor prognosis in these de nove Ph-positive MDS cases.Six cases of secondary Ph-positive MDS [28,29,[31][32][33][34] and two cases of de nove Ph-positive MDS (case 1# and this case) exhibited leukocytosis and were hypercellular with myeloid preponderance similar to CML in the disease course of transformation.Most of them progressed into AL.In this case, the subclones of BCR::ABL increased from 3% to 21.4% by FISH during the progressive phase to CML.This was assumed to stimulate cell proliferation and contribute to leukemogenesis as the production of BCR::ABL fusion protein showed strong tyrosine kinase activity [28].Of note, more acquired myelodysplasia-related CAs remained dominant clones during this phase.FISH and RT-PCR further confirmed that the positive rate of BCR::ABL was only 9% and 0.569% during the progressive phase to AML.Unfortunately, CC was not successful in this phase.
BCR::ABL fusion gene in MDS, which could benefit from TKI therapy, should be recognized as soon as possible, given its aggressiveness with an adverse prognosis and a typical poor response to conventional chemotherapy.Sheets et al. [35] recommended conducting FISH analysis for the detection of t(9;22) in patients whose CC is not readily assessable or those with normal karyotypes.Three cases of cryptic Ph MDS were verified to be positive for BCR::ABL by FISH and/or PCR.FISH with a locus-specific dual-color, dual-fusion BCR::ABL probe not only confirmed the presence of t(9;22) but also showed typical or atypical signal patterns [36].In this case, the karyotypes in 4 cells of newly diagnosed of MDS were identified as two derivative chromosoms: der(9)t(9;17), der(22)t (9;22), and long arm of chromosome 17 attached fragment of unknown origin.FISH confirmed the presence of 3% BCR/ABL atypical fusion signal (2R2G1Y), indicating the final karyotype should be a three-way variant translocation of 46,XY,t (9;22;17),inc[cp4]/46,XY [16], 17q additional fragment was from chromosome 22.
However, it is different from the broad consensus that TKIs can lead to high and durable response rates and extended OS in CML patients.Controversies were continuing regarding whether treatment with TKIs alone was better than chemotherapy in patients with Ph-positive AML or MDS [37].Additionally, cytopenia in Ph-positive MDS patients brings difficulty to the upfront administration of TKI therapy.Drummond et al. [21] reported that case 8# showed a cytogenetic complete remission (cCR) to imatinib at 600 mg daily within three months and a molecular CR (mCR) at 14 months from transformed AML.In this case, CC at diagnosis showed the dominant clones of 29/30 (96.7%)Ph-positive without additional CAs.Armas et al. [24] reported that case 12# showed an mCR to Dasatinib at 20 mg orally daily, but the patient chose hospice care after developing pneumonia which resulted in respiratory failure after seven months of follow-up.In this case, CC showed that 4/20 (20%) of cells were Ph-positive without additional CAs.Reap et al. [30] reported an mCR to imatinib therapy within three months in a case of initial MDS with normal clonal karyotypes progressing into CML two years later.With nilotinib 400 mg twice daily after progression to AML, the patient maintained a major molecular response without recurrence.Interestingly, these three cases had the dominant clones of Ph without additional CAs, which might correlate to better of TKI treatment.However, the presence of Ph with additional CAs at baseline in CML was confirmed with a poor rate of response to TKIs.[38] Drummond et al. [21] advocated that imatinib should be used as a method of effectively treating this rare malignancy.The response to imatinib was similar to many chronic-phase CML patients who achieved a cCR: An initial fall in blood counts reached a nadir, which was followed by a slow recovery.In this case series study, the progression-free survival of cases 2# and 14# was 45 and six months, respectively.It seems to indicate that the influence of Ph subclones on the prognosis of MDS depends on clonal evolution, hemocytopenia and blast count [1,26].Nevertheless, several cases of Ph-positive MDS were reported as non-response to TKIs [14,28,29,39,40] or TKI discontinued due to the worsening of cytopenia [22,33] The patient in this study was treated with imatinib at the stage of transformation to CML and showed a hematological response.However, he progressed rapidly into AML after the withdrawal of TKIs.The subclones of BCR::ABL decreased from 20% to 9% during the progressive phase to AML.More dominant clones of myelodysplasia-related supported transformation from MDS to AML rather than CML-blastic phase (BP).Transformation similar to those in CML may represent further evidence of multistep pathogenesis of leukemogenesis.
Because of comorbidities and poor performance status, the patient was evaluated as an 'unfit' patient.VEN was added with AZA, which is approved for use along with hypomethylating agents (HMAs) in the treatment of older or 'unfit' patients with newly diagnosed AMLs given comparable toxicity and improved response rates when compared with HMAs alone [41].MRD monitoring showed 0.01% and 0.0145% by FCM and RT-PCR in two months after the treatment to AML (May 2022).Notably, CC showed 2/20(10%) Ph/t(9;22) of metaphase cells alone without myelodysplasia-related CAs.Soon Low et al. [37] suggested that VEN plus an HMA could serve as the mainstay therapy for additional agents like TKIs which can be safely and effectively added.The patient kept PR with 7.6% blasts after five months of AZA + VEN treatment, Ph/t(9;22) positive without myelodysplasia-related CAs, and 3.66% of BCR::ABL transcript.However, AML relapsed in September 2022and the patient abandoned any treatment and detection.

Conclusion
In summary, de nove Ph-positive MDS may be an extremely rare entity just like the new entity of AML with BCR::ABL.It is worthwhile to accumulate more cases for further research.CC is the most commonly used method of confirming the presence of Ph/t(9;22) and other CAs.FISH with a BCR::ABL probe should be performed to avoid the missing of subtle changes in CC like microdeletion.In addition, PCR should be conducted to detect specific BCR-ABL transcript affection.The first case of de nove Ph-positive MDS with CK and p230 BCR::ABL fusion transcript was reported, and relevant literature was reviewed.Treatment that could benefit patients of de nove Ph-positive MDS needs more prospective studies to be investigated.Ph-positive MDS without additional CAs might be correlated with better survival of TKI treatment.AZA + VEN can benefit the transformed AML of Ph-positive MDS with CK, whose long-term prognosis however remains poor.

Table 1 .
Clinical characteristics of patients with de novo Philadelphia-positive myelodysplastic syndrome.