Sudden Extramedullary T-Lymphoblastic Blast Crisis in Chronic Myelogenous Leukemia a Nonrandom Event Associated with Imatinib?

Hematopathology / T-Ly m p h o b l a s t i c Crisis in CML a n d Imatinib

Sudden Extramedullary T-Lymphoblastic Blast Crisis in Chronic Myelogenous Leukemia A Nonrandom Event Associated With Imatinib?

Annette S. Kim, MD, PhD,1 Steven C. Goldstein, MD,2 Selina Luger, MD,2 Vivianna M. Van Deerlin, MD, PhD,1 and Adam Bagg, MD1 Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 Key Words: Chronic myelogenous leukemia; Sudden blast crisis; Precursor T lymphoblastic leukemia/lymphoma; Imatinib

DOI: 10.1309/GTGTEQAFMV30W753

Abstract The disease course of chronic myelogenous leukemia Imatinib has dramatically altered the natural (CML) is typically described as occurring in 3 phases: chronic history of chronic myelogenous leukemia (CML), with phase, accelerated phase, and blast crisis. The resultant acute the majority of patients now experiencing long-term leukemias are more often myeloid (~70% of cases) than lym- remission and improved survival. However, in addition phoid (~30% of cases).1 No matter what the lineage of the to the well-described phenomenon of resistance to acute transformation, the hallmark BCR/ABL1 fusion gener- imatinib, typically due to point mutations, uncommon ated by the t(9;22) in CML is invariably present in the acute consequences (eg, the development of Philadelphia leukemic cells as well, thus documenting true clonal evolution. chromosome–negative clones) may infrequently Of the lymphoid cases, the vast majority are of B-cell lineage, occur. We report 2 cases of sudden BCR/ABL1+ with only few (<50 cases) reports of cases with a precursor T blast crisis in patients with CML who had achieved immunophenotype.1,2 Precursor T blast crisis may manifest complete hematologic remission with imatinib therapy within the marrow or external to the marrow, with predomi- but were obligated to discontinue therapy owing to nantly extramedullary acute transformation (<30% bone mar- pancytopenia. These sudden blast crises were unusual row involvement at time of blast crisis) occurring in a significant at 3 levels: first, they were of precursor T lymphoblastic number of cases (9/25 cases [36%]1 and 22/44 cases [50%]2 in 2 lineage; second, they had a primary extranodal overlapping retrospective reviews of the literature) of precursor presentation without overt bone marrow involvement; T blast crisis reported to date. The occurrence of sudden blast and third, they developed after recent cessation crisis (SBC), variably defined as blast crisis following 3 months of imatinib. These observations suggest that the of complete hematologic or cytogenetic remission without an occurrence of 2 such rare cases in a single institution intervening accelerated phase, is rare, developing at a rate of within a 1-year time frame may reflect another unusual 0.4% to 2.6% by 3 years after interferon-based therapy.3 consequence of imatinib therapy. Since its introduction more than 6 years ago, imatinib has quickly become first-line therapy for CML, with the attainment of complete hematologic remission in 95% of cases, major cytogenetic remission rates of 75% to 80%, and major molecular response rates of 45% to 55%.4-6 However, this success story is not without occasional untoward effects. For example, in addition to the development of resistance to imatinib, most often due to point mutations in the tyrosine kinase domain of the ABL1 gene, there are reports of additional cytogenetic abnormalities developing in patients achieving complete cytogenetic remission based on the absence of the Philadelphia chromosome,

© American Society for Clinical Pathology Am J Clin Pathol 2008;129:639-648 639 639 DOI: 10.1309/GTGTEQAFMV30W753 639 Kim et al / T-Ly m p h o b l a s t i c Crisis in CML a n d Imatinib with this phenomenon possibly due to imatinib.7 Furthermore, supraclavicular lymph node. Excisional biopsy revealed precur- during this time, several small series or single case reports of sor T-cell lymphoblastic leukemia/lymphoma (T-ALL). A CBC SBC have been published.1,2,8 However, the incidence of SBC count obtained at that time demonstrated continued hematologic seems to be only modestly increased (3.7%) in patients treated remission with resolution of the pancytopenia.10 A bone marrow with imatinib compared with patients not treated with imatinib.9 study did not demonstrate morphologic features consistent with Herein, we report the unusual extramedullary presentation of CML, and there was neither morphologic nor immunopheno- SBC as precursor T-cell lymphoblastic lymphoma in 2 patients typic evidence of T-ALL. The patient was subsequently treated who had recently ceased imatinib therapy. These cases high- with systemic chemotherapy (CHOP: cyclophosphamide, doxo- light the possibility that cessation of imatinib may predispose rubicin [Adriamycin], vincristine, and prednisone) and attained to distinct presentations of blast crisis. complete remission. Peripheral blood cell counts remained normal for more than 9 months following blast crisis. Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021

Case Reports Case 2 Clinical and therapeutic data for the cases are summa- A 32-year-old woman was diagnosed with CML, chronic rized in zTable 1z, and hematologic data are summarized in phase, in November 2005. She was treated with 400 mg/d zTable 2z. of imatinib with attainment of hematologic remission after 2 months. However, 1 month later, a routine CBC count revealed Case 1 pancytopenia, and the imatinib was discontinued. The cell A 72-year-old man was diagnosed with CML, chronic counts began to recover, but within 1 month of stopping the phase, in February 2006. He was treated with 400 mg/d of imatinib, the patient noted an enlarging left supraclavicular imatinib and attained hematologic remission. However, after mass. This enlarged lymph node was subsequently excised and 4 months, the drug was stopped owing to the development of revealed T-ALL. A concurrent bone marrow biopsy demon- pancytopenia. After 1 month without imatinib or any other strated “minimal” (<5%) involvement by T-ALL, identifiable therapy, the patient developed an enlarged 1.5-cm left only by immunohistochemical analysis of the bone marrow

zTable 1z Clinical and Therapeutic Characteristics of Patients

CML Diagnosis– Duration of Imatinib Discon- Case No./ Diagnosis of SBC Interval Imatinib tinuation–SBC Sex CML (Phase) (mo) Therapy (mo) Interval (mo) Site of SBC Outcome

1/M Chronic 5 3.5 1.5 Left supraclavicular Good response to systemic lymph node chemotherapy for palliation 2/F Chronic 4 2.5 1.5 Left supraclavicular Good initial response to systemic lymph node chemotherapy followed by allogeneic BMT; relapse 1 mo after BMT; died 3 mo thereafter

BMT, bone marrow transplantation; CML, chronic myelogenous leukemia; SBC, sudden blast crisis. zTable 2z Summary of Hematologic Findings at Various Phases of Chronic Myelogenous Leukemia

At Hematologic At Discontinuation Case No./Variable At Diagnosis Remission of Imatinib At SBC

1 WBC count, /µL (× 109/L) 426,900 (426.9) 6,000 (6.0) 1,700 (1.7) 3,900 (3.9) Hemoglobin level, g/dL (g/L) 11.1 (111) 11.4 (114) 11.6 (116) 13.3 (133) Platelet count, × 103/µL (× 109/L) 92 (92) 86 (86) 37 (37) 189 (189) Blasts, % 0 0 0 0 2 WBC count, /µL (× 109/L) 233,700 (233.7) 6,700 (6.7) 3,600 (3.6) 2,600 (2.6) Hemoglobin level, g/dL (g/L) * 10.8 (108) 11 (110) 11.3 (113) Platelet count, × 103/µL (× 109/L) 278 (278) 359 (359) 127 (127) 384 (384) Blasts, % 0 0 0 0

SBC, sudden blast crisis. * Hematocrit value, 38% (0.38).

640 Am J Clin Pathol 2008;129:639-648 © American Society for Clinical Pathology 640 DOI: 10.1309/GTGTEQAFMV30W753 Hematopathology / Original Ar t i c l e biopsy specimen; there were no morphologic features consis- sulfonic acid/ethylene glycol tetraacetic acid (Hepes/EGTA) tent with CML. The patient was treated with intensive systemic hypotonic solution and exposure to colchicine for 55 minutes chemotherapy (hyper-CVAD: cyclophosphamide, methotrex- (10 µg/mL). The cells were then fixed in methanol/acetic ate, doxorubicin, vincristine, dexamethasone, and cytarabine) acid before preparation of slides and G banding with trypsin- for 2 rounds before undergoing allogeneic bone marrow trans- Giemsa. plantation. Unfortunately, however, the T-ALL recurred in the central nervous system 1 month later, and the patient died of Fluorescence In Situ Hybridization progressive disease 4 months after transplantation. Cells were treated for 30 minutes in medium before suspension in a Hepes/EGTA hypotonic solution for 35 minutes. Cells were then fixed in methanol/acetic acid before preparation of slides. Slides then were denatured, and the dual-color BCR/ Materials and Methods Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 ABL1 translocation DNA probe set (Vysis, Downers Grove, IL) was applied to examine interphase nuclei. Fluorescence in situ Morphologic Studies hybridization (FISH) was performed according to the manufac- Peripheral blood smears and bone marrow aspirate smears turer’s recommendations and photographed with a fluorescence were air dried and stained with Wright-Giemsa. Bone marrow microscope using a tricolor filter. Normal cells were expected biopsy specimens were fixed in B-5, decalcified, and embed- to display 2 green (BCR gene) signals and 2 orange (ABL1 ded in paraffin. Sections (5 µm) were obtained and stained gene) signals. Positive nuclei were expected to display 1 green, with H&E. Clot sections were fixed in B-5 and embedded 1 orange, and 1 yellow signal that resulted from the fused BCR/ in paraffin. Sections (5 µm) were obtained and stained with ABL1 gene. Five hundred nuclei were counted, and the percent- H&E. Lymph node specimens were fixed in B-5 and formalin age of positive fusion signals (yellow signals) was calculated. and embedded in paraffin. Sections (5 µm) were obtained and stained with H&E. BCR/ABL1 Fusion Transcript Analysis RNA was extracted from peripheral blood and bone mar- Flow Cytometry row aspirate samples using RNeasy columns according to the Cells from bone marrow aspirate and lymph node speci- manufacturer’s procedure (Qiagen, Valencia, CA). Formalin- mens were analyzed by flow cytometry. Fresh, unfixed lymph fixed, paraffin-embedded lymph node samples were deparaf- node specimens were mechanically disaggregated before finized with Citirisolv (Thermo Fisher Scientific, Waltham, analysis. Immunophenotyping was performed using 4-color MA) followed by overnight digestion at 50°C with 180 µg of flow cytometric analysis (FACScan flow cytometer, Becton Proteinase K in 250 µL of 20 mmol/L of tris(hydroxymethyl) Dickinson, San Jose, CA) according to standard protocol. The aminomethane hydrochloride, pH 8; 20 mmol/L of EDTA; following directly conjugated monoclonal antibodies (Becton and 1% sodium dodecyl sulfate. RNA extraction from the Dickinson) were used: CD3, CD4, CD5, CD7, CD8, CD10, lysate was performed with Trizol-LS (750 µL) as indicated CD11c, CD19, CD20, CD22, CD23, CD45, κ, and λ. Flow by the manufacturer (Invitrogen, Carlsbad, CA). Qualitative cytometric data were analyzed by using CellQuest software reverse transcription–polymerase chain reaction (RT-PCR) (Becton Dickinson). analysis for the BCR/ABL1 fusion transcript was performed in a 2-step reaction using 1 µg of each RNA sample to make Immunohistochemical Analysis complementary DNA with Maloney murine leukemia virus Immunohistochemical analysis was performed on 5-µm reverse transcriptase. After the reverse transcription step, 3 PCR sections from the bone marrow and lymph node biopsies. The reactions were performed using primers that detect the e13a2/ EnVision+ horseradish peroxidase system (DAKO, Carpinteria, e14a2 and e1a2 fusion transcripts, as well as primers for the

CA), mouse or rabbit, was used for antibody staining. The fol- β2-microglobulin transcript, used as a control for sample qual- lowing antibodies were used: CD1a, CD2, CD3, CD7, and ity. Amplification products were separated by 2% agarose gel CD10 (Vision BioSystems Novocastra Laboratories, Norwell, electrophoresis in 1× Tris-borate EDTA and visualized with MA); CD8, CD45, terminal deoxynucleotidyl transferase ethidium bromide. Appropriate positive and negative control (TdT), and BCL2 (DAKO); CD4 (Biocare, Concord, CA); samples were used. CD5 (NeoMarkers, Fremont, CA); and CD34 (BD Biosciences, San Jose, CA). T-Cell Receptor γ Gene Rearrangement Analysis by PCR DNA was extracted from peripheral blood by using the Cytogenetic Analysis MagAttract M48 BioRobot with MagAttract DNA Blood Midi For cytogenetic studies, cells were cultured for 24 hours M48 Kit (Qiagen) and from bone marrow aspirate by using before suspension in a 4-(2-hydroxyethyl)-1-piperazineethane- the QIAamp Blood Kit (Qiagen). DNA from formalin-fixed,

© American Society for Clinical Pathology Am J Clin Pathol 2008;129:639-648 641 641 DOI: 10.1309/GTGTEQAFMV30W753 641 Kim et al / T-Ly m p h o b l a s t i c Crisis in CML a n d Imatinib paraffin-embedded lymph node tissue was obtained by deparaf- Biosystems). Interpretive criteria for the presence of a mono- finization with xylene followed by Proteinase K digestion (720 clonal population were as previously described.11 µg) in Qiagen ATL buffer overnight at 56°C. After an RNase digestion step, the DNA was extracted using QIAamp spin col- Results umns according to the manufacturer’s suggestion. PCR amplification of the T-cell receptor γ chain (TRG@) gene was per- Case 1 formed in 2 mixtures of fluorescently labeled primers that cover all possible Vγ (Vγ1-8 and Vγ9-11) and Jγ (Jγ1/Jγ2, JγP1/JγP2, Lymph Node 11 and JγP) combinations as previously described. Amplification H&E-stained sections of the left supraclavicular mass products were separated by capillary gel electrophoresis on revealed an enlarged lymph node (1.5 cm) partially effaced by an Applied Biosystems 3130XL (Applied Biosystems, Foster a diffuse infiltrate with scattered subcortical residual germinal Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 City, CA) according to the manufacturer’s protocol. Data anal- centers zImage 1Az and zImage 1Bz. The infiltrate was com- ysis was performed with GeneMapper 3.7 software (Applied posed of numerous medium-sized blasts with large oval to

A B

C D

zImage 1z (Case 1) Lymph node and bone marrow findings at sudden blast crisis. A, Lymph node showing partial effacement of lymph node architecture with evidence of extension beyond the capsule (H&E, ×2.5). B, Lymph node showing medium-sized blasts (H&E, ×40). C, Bone marrow biopsy specimen showing a mildly hypercellular marrow with trilineage hematopoiesis (H&E, ×20). D, Bone marrow aspirate demonstrating maturing hematopoiesis (Wright-Giemsa, ×100).

642 Am J Clin Pathol 2008;129:639-648 © American Society for Clinical Pathology 642 DOI: 10.1309/GTGTEQAFMV30W753 Hematopathology / Original Ar t i c l e irregular nuclei, vesicular chromatin, inconspicuous nucleoli, of identical size (184 bp) was also present in the bone marrow and scant cytoplasm. and peripheral blood. Flow cytometry was not performed on this lymph node specimen. However, paraffin immunohistochemical analysis Bone Marrow demonstrated that the neoplastic cells were CD1a+, CD2–, The concurrent bone marrow specimen revealed a mild- CD3–, CD4+, CD5+, CD7+, CD8–/+, CD10–, CD34+, TdT+, ly hypercellular marrow (~40% cellularity) with trilineage and BCL2+. hematopoiesis and no overt morphologic evidence of involve- RT-PCR analysis for a BCR/ABL1 fusion transcript iden- ment by T-ALL or CML zImage 1Cz and zImage 1Dz. Flow tified the presence of the e14a2 fusion transcript in the lymph cytometry performed on the bone marrow aspirate failed to node. In addition, TRG@ gene rearrangement studies by PCR reveal any immunophenotypic evidence of involvement by revealed the presence of a minor 184-base-pair (bp) peak T-ALL. Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 using the Vγ 9-11 primers within a predominantly polyclonal Cytogenetics performed on the bone marrow specimen background zImage 2Cz. Although this peak did not, in isola- demonstrated a complex karyotype with the t(9;22) in addition, meet strict criteria for monoclonality, a monoclonal peak tion to other abnormalities zTable 3z. In addition, RT-PCR

A 160 170 180 190 200 210 bp 5,000 4,000 3,000 RFU 2,000 1,000 0 sz 184.46 sz 194.09 ht 5,122 ht 1,577

160 170 180 190 200 210 bp 7,000 6,000 5,000 4,000 RFU 3,000 2,000 1,000 0 sz 184.52 sz 194.11 ht 7,161 ht 2,641

160 170 180 190 200 210 bp 600 500 400

RFU 300 200 100 0 sz 182.26 sz 186.34 ht 88 ht 197 sz 184.41 ht 471 zImage 2z (Case 1) T-cell receptor γ chain gene rearrangement studies using Vγ9-11 primers. A, Peripheral blood. Dominant 184-base-pair (bp) peak and lesser 194-bp peak identified. B, Bone marrow aspirate. Dominant 184-bp peak and minor 194-bp peak identified. C, Lymph node. Equivocal 184-bp peak identified within a polyclonal background. ht, height; RFU, relative fluorescence units; sz, size.

© American Society for Clinical Pathology Am J Clin Pathol 2008;129:639-648 643 643 DOI: 10.1309/GTGTEQAFMV30W753 643 Kim et al / T-Ly m p h o b l a s t i c Crisis in CML a n d Imatinib zTable 3z Summary of Genetic Findings at Various Phases of Chronic Myelogenous Leukemia

Specimen Type (at SBC)

Case No./Test Diagnosis of CML Lymph Node Peripheral Blood Bone Marrow

1 BCR/ABL1 RT-PCR +* e14a2 +* e14a2 BCR/ABL1 FISH ND ND ND ND Cytogenetics ND ND ND 46,XY,t(9;22)(q34;q11.2)[21]/59, XXYY,idem,add(1)(p32),+4,+6,+8, add(9)(p13),+10,+11,+14,+21, +22,[cp16]/46,XY[18] TRG@-PCR ND + + + 2 Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 BCR/ABL1 RT-PCR ND e13a2 and e1a2 e13a2 and e1a2 ND BCR/ABL1 FISH 91.5% +† ND 86%+ ND Cytogenetics 46,XX,der(8)t(8;9;22)(p21;q34; 46,XX[11] 46,XX[11] 46,XX,?add(8)(p21),t(9;22) q11.2),der(9)del(9)(p13p22) (q34;q11.2)[1]/44,XX,idem, t(8;9;22)(p21;q34;q11.2), –6,–19[1]?; duplication der(22)(t;8;9;22)(p21;q34; of 9q34 q11.2)[20]† TRG@-PCR ND ND ND ND

FISH, fluorescence in situ hybridization; ND, not done; RT-PCR, reverse transcription–polymerase chain reaction; SBC, sudden blast crisis; TRG@, T-cell receptor γ chain. * Quantitative RT-PCR performed on peripheral blood. † Performed on peripheral blood.

analysis identified the presence of the e14a2 BCR/ABL1 fusion transcripts. TRG@ gene rearrangement studies were fusion transcript. TRG@ gene rearrangement studies of the not performed owing to tissue exhaustion. bone marrow aspirate revealed the presence of a monoclonal T-cell rearrangement, with peaks of 184 and 194 bp, using the Bone Marrow

Vγ 9-11 primers zImage 2Bz. The peripheral blood, which was A staging bone marrow biopsy was performed and similarly morphologically negative for involvement by ALL revealed a hypocellular marrow (~25% cellularity) with trilin- (flow cytometry not performed), was also positive for the 184- eage hematopoiesis zImage 3Cz. There was no morphologic and 194-bp PCR products zImage 2Az. evidence consistent with CML. Although there was no overt morphologic evidence of involvement by lymphoma, immu- Case 2 nohistochemical stains identified 30% small CD3(variable)+, CD4+ lymphocytes and approximately 5% CD1a(weak)+ Lymph Node cells zImage 3Dz. Excisional biopsy of the left supraclavicular lymph node Cytogenetics performed on the bone marrow aspirate revealed an enlarged node (2.0 cm) with complete effacement showed a complex karyotype with the t(9;22) and evidence of nodal architecture by a diffuse infiltrate composed of medi- of clonal evolution (Table 3). Conventional cytogenetics um-sized blastic cells with round nuclei, slightly condensed performed on a tandem peripheral blood specimen, which chromatin, inconspicuous nucleoli, and scant cytoplasm zIm- showed no hematologic evidence of CML, demonstrated a age 3Az and zImage 3Bz. Mitoses and apoptotic cells were normal female karyotype; however, interphase FISH and readily identifiable. RT-PCR were positive for a BCR/ABL1 fusion. The former Flow cytometry performed on representative fresh tissue was positive in 86% of the nuclei and the latter revealed the demonstrated an expansion (~94% of total events) of cells e13a2 and e1a2 fusion transcripts. TRG@ gene rearrangement with the following immunophenotypic profile: CD2+, surface studies were not done. CD3–, CD4+, CD5+, CD7(dim)+, and CD8–. Paraffin immunohistochemical analysis revealed that the neoplastic cells were CD1a(bright)+, CD3(bright)+, CD4+, CD5+, CD8–, Discussion CD10–, CD34–, CD45(weak)+, and TdT+. Cytogenetics performed on the lymph node tissue dem- We identified 2 unusual cases of SBC in patients with onstrated a normal female karyotype. RT-PCR analysis for the CML. The 3 salient features that distinguish these 2 cases from BCR/ABL1 fusion transcript performed on the formalin-fixed the prototypic progression of CML to blast crisis are: (1) the lymph node, however, was positive for the e13a2 and e1a2 rather short interval (~1 month) between cessation of imatinib

644 Am J Clin Pathol 2008;129:639-648 © American Society for Clinical Pathology 644 DOI: 10.1309/GTGTEQAFMV30W753 Hematopathology / Original Ar t i c l e

A B Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021

C D

zImage 3z (Case 2) Lymph node and bone marrow findings at sudden blast crisis. A, Lymph node showing complete effacement of lymph node architecture (H&E, ×2.5). B, Lymph node showing medium-sized blasts (H&E, ×20). C, Bone marrow biopsy specimen demonstrating trilineage hematopoiesis and scattered lymphoid cells (H&E, ×20). D, Bone marrow biopsy specimen demonstrating ~30% CD4+ cells (CD4, ×20). therapy and development of SBC; (2) the T-cell, rather than elsewhere but seen at our institution for the first time. The the more common [in the context of lymphoid transformation] majority of these patients were receiving imatinib therapy. B-cell, lineage of the blasts; and (3) their primary, and essen- We encountered 5 cases of blast transformation, with 4 tially exclusive, extramedullary presentation. being SBCs, during this period. It is interesting that although The 2 patients were identified during the 12-month the single case of blast crisis evolving through an acceler- period from November 2005 through October 2006. Clinical ated phase was of myeloid lineage, all 4 cases of SBC were and pathology databases for this period were searched to lymphoblastic, 2 each of B and T lineage, with the 2 T-ALLs determine the total number of CML cases seen and for diag- notable for their extramedullary presentations. Although the noses of blast crisis. During this period, there were approxi- nature of the ascertainment of the data precludes a rigorous mately 65 new CML patient visits to the Hematology- assessment of the significance of these findings, these obser- Oncology Clinic of the University of Pennsylvania Health vations suggest an unexpected bias toward lymphoblastic, System, Philadelphia. This number includes patients with in particular T lymphoblastic, SBC in patients with CML newly diagnosed CML and patients with CML diagnosed treated with imatinib.

Until the advent of imatinib therapy, CML followed a and one biclonal. A retrospective analysis of cases of SBC rather predictable course, albeit with heterogeneous symp- from the literature found that 4 of 7 SBC cases were of lym- tomatology and variability in progression.12 The course typi- phoid lineage.9 Thus, there seems to be not only an increase cally spanned 3 phases: chronic, accelerated, and blast. The in the incidence of SBC with imatinib (within the limitations majority of cases (~85%) were, and still are, diagnosed during of the aforementioned studies) but also a shift from myeloid the chronic phase. However, without imatinib, approximately predominance to roughly equivalent numbers of myeloid and 3 to 5 years after diagnosis, the disease underwent an inexo- lymphoid SBCs. These findings are in keeping with the lym- rable progression to accelerated and, finally, blast phases. phoid predominance noted previously in cases of SBC, with The accelerated phase has been variably defined and 1 recent study noting lymphoid cases to outnumber myeloid consists of a gradation of the features (especially blast count) leukemias by 2-fold, a striking reversal of the ratio evident in between chronic phase and that of blast phase including 10% gradual blast crisis.3 Of note, only 10% of patients in the study Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 to 19% blasts in the peripheral blood or bone marrow, 20% were treated with imatinib,3 suggesting that lymphoblastic or more peripheral blood basophils, persistent thrombocy- leukemias may more commonly manifest as a sudden rather topenia unrelated to therapy or persistent thrombocytosis than gradual blast crisis, unrelated to therapy. unresponsive to therapy, increasing WBC count and spleen Of the cases of lymphoid SBC in patients receiving size unresponsive to therapy, and cytogenetic evidence of imatinib with published immunophenotypic data, 2 of 2 cases clonal evolution.13 Gene microarray studies have suggested were of B-cell origin.16,17 The remaining 4 published cases of that the accelerated phase is not truly a separate phase, but lymphoid SBC did not include data sufficient to designate the rather a period of transition during which the genetic altera- cell of origin as T or B.9,18 In all cases, the SBC was evident in tions propelling the blast crisis have already occurred and the marrow and peripheral blood. Thus, the 2 cases presented are beginning to exert their tumorigenic influence.14 At the herein are unique in their T-cell immunophenotype and their point of acceleration, and indeed often before this stage, extramedullary site of involvement with minimal to no con- accumulation of additional genetic aberrations in addition to comitant bone marrow or peripheral blood disease. However, the initiating pathogenic BCR/ABL1 fusion transcript have although neither case had overt medullary or circulating been noted. The most prevalent aberrations include trisomy 8, disease, “minimal disease” was evident molecularly in the isochromosome i(17q), trisomy 19, and an extra Philadelphia marrow and blood of case 1 and possibly in the bone marrow chromosome (duplication of the Philadelphia chromosome).12 of case 2. These data, together with the BCR/ABL1 FISH and Nevertheless, the incidence of progression directly from the RT-PCR analyses, indicate that although the SBC in these chronic phase to blast phase without an intervening acceler- patients manifested extramedullary, there was (minimal) evi- ated phase (ie, SBC) was rare, at a rate of 0.4% to 2.6% by 3 dence of clonal evolution in the blood and/or bone marrow. years after interferon-based therapy regimens.3 The rather unimpressive TRG@ peak in the lymph node of In “gradual” blast crisis, the majority (~70%) of cases are case 1, as compared with the rather robust peaks in the blood of myeloid lineage.12 Only approximately 30% of cases are and marrow, is likely due to a combination of partial involve- lymphoblastic. The nature of the blasts in the acute leukemia ment of the lymph node and lack of competing polyclonal T phase has been critical in directing therapy decisions. Of the cells in the blood and marrow. lymphoblastic leukemias, those of B-cell lineage have pre- The molecular finding of the BCR/ABL1 fusion in the dominated, with only rare case reports (<50 cases) of T-cell sites of extramedullary blast crisis, in both cases a left supra- lymphoblast lineage.1,2,8 As with de novo acute lymphoblas- clavicular lymph node, is highly suggestive of the T-ALL tic leukemias, the majority of cases present with circulating having derived from the original CML. Cytogenetics of the blasts and bone marrow involvement, although extramedul- morphologically negative bone marrow samples at the time lary presentations (in isolation or with concurrent or near of SBC are complex with numerous aberrations. Indeed, both concurrent bone marrow involvement of <30% of cellularity) cases demonstrated evidence of aberrations in chromosome are not uncommon and were found in 36% to 50% of cases 8 at transformation, a finding noted in other cases of SBC.18 reviewed.1,2,8,15 Unfortunately, diagnostic cytogenetics were not performed at The cases presented herein clearly followed a different the outside hospital where case 1 was initially diagnosed, and clinical course. The absence of an accelerated phase has been case 2 demonstrated evidence of similar chromosome 8 aber- termed SBC.3 With the advent of imatinib treatment, several rancies at diagnosis. It would have been of interest to deter- studies have suggested a modest increase in the numbers of mine if those complex chromosomal abnormalities, including SBCs, previously quite rare. In 1 study, 6 of 164 patients the aberrations in chromosome 8, were newly acquired in case with CML underwent SBC within 35 months from diagnosis, 1 at the time of SBC. representing approximately 3.7% of cases and 54.5% of cases The accumulation of additional cytogenetic aberrations that underwent blast crisis.9 Of the 6 cases, 2 were lymphoid has been commonly associated with blast crisis in CML. It has

646 Am J Clin Pathol 2008;129:639-648 © American Society for Clinical Pathology 646 DOI: 10.1309/GTGTEQAFMV30W753 Hematopathology / Original Ar t i c l e been hypothesized that although some of the genetic changes onset, rather than to imatinib itself. However, the use of may mediate the blast crisis, others may merely be a mani- imatinib has been associated with a hint of a mild increase in festation of the genomic instability caused by the BCR/ABL SBC,9 and so imatinib may result secondarily in an increase fusion product.19 Thus, BCR/ABL1 promotes CML not only in lymphoblastic transformations. through its pathogenic role in proliferation and antiapoptosis, We have presented 2 cases of extramedullary but also through the creation of an unstable genetic environ- T-lymphoblastic transformation in patients previously in ment. complete hematologic remission from CML. The use of im- Theoretically, the lower the level of BCR/ABL1, the atinib or its cessation may be responsible in these cases for the less likely the case should be to go on to blast crisis. Hence, disease transformation, although there is no mechanistic data the apparent mild increase in cases of BCR/ABL1+ SBC in or statistical power at this time to support such hypotheses. patients treated with imatinib seems paradoxical. This may However, the unusual presentation of these 2 cases within a Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 be due to the direct inhibition by imatinib of ephrin-mediated short period at a single institution prompts the speculation that tumor suppressor effects, although this antitumor suppressor they may be indicative of a trend toward more atypical blast effect to date has not been linked to an increased incidence of crises in patients treated with imatinib. neoplasms (hematopoietic or nonhematopoietic) in patients receiving imatinib therapy.20,21 Alternatively, the resurgence From the Departments of 1Pathology and Laboratory Medicine 2 of a hematopoietic clone may be secondary to the acquired and Hematology Oncology, Hospital of the University of Pennsylvania, Philadelphia. refractoriness to imatinib therapy, through acquisition of point mutations making imatinib ineffective or through the develop- Supported by a SCOR grant from the Leukemia and ment of BCR/ABL1– clones.12,22-24 However, in the 2 present Lymphoma Society of America, White Plains, NY (Dr Bagg). Address reprint requests to Dr Bagg: Dept of Pathology and cases, the presence of the BCR/ABL1 clone suggests that this Laboratory Medicine, Hospital of the University of Pennsylvania, latter explanation is not relevant to them. The reasons for the 7.103 Founders Pavilion, 3400 Spruce St, Philadelphia, PA observed association with T-cell, as opposed to the prototypic 19104. B-cell, lymphoid blast crisis and the extramedullary location are enigmatic. It is interesting that both patients, after achieving a hema- References tologic complete response, stopped imatinib treatment sec- 1. Ye CC, Echeverri C, Anderson JE, et al. T-cell blast crisis ondary to cytopenias. In both cases, within 1.5 months, SBC of chronic myelogenous leukemia manifesting as a large mediastinal tumor. Hum Pathol. 2002;33:770-773. occurred. It is, therefore, tantalizing to speculate that progres- 2. Raanani P, Trakhtenbrot L, Rechavi G, et al. Philadelphia- sion to SBC may have been due to a rapid resurgence of BCR/ chromosome-positive T-lymphoblastic leukemia: acute ABL1 function and unfettered genetic instability, leading to leukemia or chronic myelogenous leukemia blastic crisis. blast crisis. However, this thesis is difficult to reconcile with Acta Haematol. 2005;113:181-189. the findings of several studies that found the reemergence of 3. Kantarjian H, O’Brien S, Cortes J, et al. Sudden onset of the blastic phase of chronic myelogenous leukemia. Cancer. the BCR/ABL1 clone after discontinuation of imatinib but not 2003;98:81-85. 25-30 an associated increased incidence of SBC. Unfortunately, 4. Hughes T, Deininger M, Hochhaus A, et al. Monitoring neither patient was followed up (at an outside institution or CML patients responding to treatment with tyrosine kinase internally) by quantitative BCR/ABL1 during hematologic inhibitors: review and recommendations for harmonizing current methodology for detecting BCR-ABL transcripts and remission and cessation of imatinib, although case 1 was kinase domain mutations and for expressing results. Blood. evaluated by RT-PCR at initial diagnosis of CML and imme- 2006;108:28-37. diately after diagnosis of a lymphoblastic lymphoma. One can 5. O’Brien SG, Guilhot F, Larson RA, et al. Imatinib compared speculate that the patients might have undergone an increase with interferon and low-dose cytarabine for newly diagnosed chronic-phase chronic myeloid leukemia. N Engl J Med. in BCR/ABL1 clones after cessation of imatinib therapy, 2003;348:994-1004. which resulted in the SBCs. 6. Druker BJ, Guilhot F, O’Brien SG, et al. Five-year follow-up Alternatively, there is no evidence to refute the hypoth- of patients receiving imatinib for chronic myeloid leukemia. esis that molecular relapse did not precede the discontinua- N Engl J Med. 2006;355:2408-2417. tion of imatinib. This latter possibility suggests that perhaps 7. Jabbour E, Kantarjian HM, Abruzzo L, et al. Chromosomal abnormalities in Philadelphia chromosome–negative meta- the cytopenias noted at the time of imatinib discontinuation phases appearing during imatinib mesylate therapy in patients may have been the first manifestations of transformation and with newly diagnosed chronic myeloid leukemia in chronic molecular relapse before an obvious blast crisis. It is interest- phase. Blood. 2007;110:2991-2995. ing that because lymphoid blast crises seem to predominate 8. Dorfman DM, Longtine JA, Fox EA, et al. T-cell blast crisis 3 in chronic myelogenous leukemia; immunophenotypic during SBC regardless of therapy, the lymphoblastic nature and molecular biologic findings. Am J Clin Pathol. of these 2 cases may be due to their apparently precipitate 1997;107:168-176.

9. Alimena G, Breccia M, Latagliata R, et al. Sudden blast 21. Noren NK, Foos G, Hauser CA, et al. The EphB4 receptor crisis in patients with Philadelphia chromosome–positive suppresses breast cancer cell tumorigenicity through an chronic myeloid leukemia who achieved complete cytogenetic Abl-Crk pathway. Nat Cell Biol. 2006;8:815-825. remission after imatinib therapy. Cancer. 2006;107:1008-1013. 22. O’Dwyer ME, Gatter KM, Loriaux M, et al. Demonstration 10. Cortes J, Talpaz M, O’Brien S, et al. Molecular responses of Philadelphia chromosome negative abnormal clones in in patients with chronic myelogenous leukemia in chronic patients with chronic myelogenous leukemia during major phase treated with imatinib mesylate. Clin Cancer Res. cytogenetic responses induced by imatinib mesylate. Leukemia. 2005;11:3425-3432. 2003;17:481-487. 11. Luo V, Lessin SR, Wilson RB, et al. Detection of clonal T-cell 23. Perel JM, McCarthy C, Walker O, et al. Clinical significance receptor gamma gene rearrangements using fluorescent-based of development of Philadelphia-chromosome negative clones PCR and automated high-resolution capillary electrophoresis. in patients with chronic myeloid leukemia treated with imatinib Mol Diagn. 2001;6:169-179. mesylate [letter]. Haematologica. 2005;90:e70-e71. Available at 12. Faderl S, Talpaz M, Estrov Z, et al. The biology of chronic www.haematologica.org/cgi/reprint/90/Suppl/ECR25. Downloaded from https://academic.oup.com/ajcp/article/129/4/639/1760114 by guest on 29 September 2021 myeloid leukemia. N Engl J Med. 1999;341:164-172. 24. Hochhaus A, Kreil S, Corbin AS, et al. Molecular and 13. Jaffe ES, Harris NL, Stein H, et al, eds. Pathology and Genetics chromosomal mechanisms of resistance to imatinib (STI571) of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, therapy. Leukemia. 2002;16:2190-2196. France: IARC Press; 2001:89-91. World Health Organization 25. Ricci C, Scappini B, Divorky V, et al. Mutation in the Classification of Tumours. ATP-binding pocket of the ABL kinase domain in an 14. Radich JP, Dai H, Mao M, et al. Gene expression changes STI571-resistant BCR/ABL-positive cell line. Cancer Res. associated with progression and response in chronic myeloid 2002;62:5995-5998. leukemia. Proc Natl Acad Sci U S A. 2006;103:2794-2799. 26. Breccia M, Diverio D, Pane F, et al. Discontinuation of 15. Jacknow G, Frizzera G, Gaijl-Peczalska K, et al. Extramedullary imatinib therapy after achievement of complete molecular presentation of the blast crisis of chronic myelogenous response in a Ph+ CML patient treated while in long lasting leukaemia. Br J Haematol. 1985;61:225-236. complete cytogenetic remission (CCR) induced by interferon. Leuk Res. 2006;30:1577-1579. 16. Avery S, Nadal E, Marin D, et al. Lymphoid transformation in a CML patient in complete cytogenetic remission following 27. Mauro MJ, Druker BJ, Maziarz RT. Divergent clinical outcome treatment with imatinib. Leuk Res. 2004;28(suppl 1):S75-S77. in two CML patients who discontinued imatinib therapy after achieving a molecular remission. Leuk Res. 2004;28(suppl 17. Morimoti A, Ogami A, Chiyonogu T, et al. Early blast 1):S71-S73. transformation following complete cytogenetic response in a pediatric chronic myeloid leukemia patient treated with 28. Merante S, Orlandi E, Bernasconi P, et al. Outcome of four imatinib mesylate. J Pediatr Hematol Oncol. 2004;26:320-322. patients with chronic myeloid leukemia after imatinib mesylate discontinuation. Haematologica. 2005;90:979-981. 18. Jabbour E, Kantarjian H, O’Brien S, et al. Sudden blastic transformation in patients with chronic myeloid leukemia 29. Rousselot P, Huguet F, Rea D, et al. Imatinib mesylate treated with imatinib mesylate. Blood. 2006;107:480-482. discontinuation in patients with chronic myelogenous leukemia in complete molecular remission for more than 2 19. Ilaria RL Jr. Pathobiology of lymphoid and myeloid blast crisis years. Blood. 2007;109:58-60. and management issues. Hematology Am Soc Hematol Educ Program. 2005:188-194. 30. Cortes J, O’Brien S, Kantarjian H. Discontinuation of imatinib therapy after achieving a molecular response [letter]. Blood. 20. Wang JYJ. Eph tumor suppression: the dark side of Gleevec. 2004;104:2204-2205. Nat Cell Biol. 2006;8:785-786.