Immunophenotype and ultrastructural studies in blast crisis of chronic myeloid leukemia

Blast phase in chronic myelogenous leukemia is skewed toward unusual blast types in patients treated with tyrosine kinase inhibitors: a comparative study of 67 cases

OBJECTIVES

To compare the features of the blast phase of chronic myelogenous leukemia (CML) in patients treated with tyrosine kinase inhibitors (TKIs) with those in the pre-TKI era.

METHODS

Sixty-seven patients with blast phase CML were identified in the Duke Pathology database from 1991 to 2011. The morphology and immunophenotype of blasts were evaluated, along with cytogenetic studies and associated findings in the peripheral blood and bone marrow.

RESULTS

In the TKI era, the blasts were more frequently of a type other than the usual myeloid or lymphoid types when compared with the pre-TKI era. Blast phase in TKI-treated patients was associated with a higher peripheral WBC count and a lower blast percentage in the bone marrow. Of the 23 patients with cytogenetic studies during blast phase, additional cytogenetic changes more frequently occurred in patients with an unusual blast type, and some patients showed these changes months before the onset of blast phase.

CONCLUSIONS

Blast phase CML in TKI- and non-TKI-treated patients differs in the morphology and immunophenotype of blasts, cytogenetic findings, and associated findings in the peripheral blood and bone marrow.

Immunophenotypic profile of acute leukemia: critical analysis and insights gained at a tertiary care center in India

BACKGROUND

To analyze the spectrum of various types and subtypes of acute leukemia.

METHODS

Two thousand five hundred and eleven consecutive new referral cases of acute leukemia (AL) were evaluated based on WHO classification.

RESULTS

It included 1,471 cases (58%) of acute lymphoblastic leukemia (ALL), 964 cases (38%) of acute myeloid leukemia (AML), 45 cases (1.8%) of chronic myelogenous leukemia in blast crisis (CMLBC), 37 cases (1.5%) of biphenotypic acute leukemia (BAL), 1 case of Triphenotypic AL, and 2 cases of acute undifferentiated leukemia (AUL). Common subtypes of ALL were B-cell ALL (76%), which comprised of intermediate stage/CALLA positive (73%), early precursor/proBALL (3%). T-cell ALL constituted 24% (351 cases) of ALL. Common subtypes of AML included AMLM2 (27%), AMLM5 (15%), AMLM0 (12%), AMLM1 (12%), APML (11%), and AML t(8;21) (9%). CMLBC was commonly of myeloid blast crisis subtype (40 cases).

CONCLUSION

B-cell ALL was the commonest subtype in children and AML in adults. Overall incidence of AML in adults was low (53% only). CD13 was most sensitive and CD117 most specific for determining myeloid lineage. A minimal primary panel of nine antibodies consisting of three myeloid markers (CD13, CD33, and CD117), B-cell lymphoid marker (CD19), T-cell marker (CD7), with CD45, CD10, CD34, and HLADR could assign lineage to 92% of AL. Cytogenetics findings lead to a change in the diagnostic subtype of myeloid malignancy in 38 (1.5%) cases.

Phenotype of blasts in chronic myeloid leukemia in blastic phase-Analysis of bone marrow trephine biopsies and correlation with cytogenetics

We identified different phenotypic subsets among 62 cases of chronic myeloid leukemia (CML) in blast crisis (BC) (26% B-lymphoblastic, and 74% various myeloblastic subsets) on bone marrow trephines and correlated the blast-phenotype with cytogenetics. Five of myeloid-BC had an associated 3q26 abnormality and two of these showed a megakaryoblastic-phenotype. While myeloid-BC was associated with additional copies of Philadelphia (Ph) (29%) (p=0.08), numerical abnormalities (51%) (p=0.007), trisomy-8 (29%) (p=0.08) and 17p-loss (22%), none of lymphoid-BC showed these abnormalities. Among myeloid-BC, CD34-negative cases were more often associated with trisomy-8, 17p-loss and numerical abnormalities, and the CD117-negative subset with additional copies of Ph (p<0.05).

New insights into the pathobiology and treatment of chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is one of the most frequently diagnosed forms of leukemia. Recent advances in the understanding of the molecular mechanisms involved in the pathogenesis of this disorder led to new diagnostic and therapeutic approaches. From a disease that used to be diagnosed purely on morphologic grounds, CML is now an entity that cannot be diagnosed in the absence of relevant cytogenetic or molecular data. Identification of the characteristic t(9;22) cytogenetic abnormality or of the BCR-ABL molecular abnormality is mandatory, as current treatment approaches rely on the use of agents active against this specific molecular target. This article presents the evolution in the understanding of the pathogenic mechanisms involved in CML, as well as the methods and the criteria currently in use in its diagnosis and treatment.

Paraplegia as the presenting manifestation of extramedullary megakaryoblastic transformation of previously undiagnosed chronic myelogenous leukemia

Extramedullary tumors, also known as granulocytic sarcomas (GS), occur most frequently in acute myelogenous leukemia (AML). They may signal the onset of the accelerated phase of chronic myelogenous leukemia (CML) or the blastic transformation of a myeloproliferative disorder. Occasionally, a GS may be the presenting sign of undiagnosed AML, and rarely the presenting sign of undiagnosed CML or aleukemic leukemia. Paraplegia due to a spinal cord GS is an extremely rare presentation of undiagnosed leukemia. This is the first case report of paraplegia as the presenting manifestation of extramedullary megakaryoblastic transformation of previously undiagnosed CML. A 53-year-old woman reported back pain for 6 days, rapidly progressing to paraplegia. Physical examination noted a large abdominal mass and flaccid paralysis in both lower extremities. Spinal MRI revealed a T4-T6 vertebral mass causing spinal stenosis and cord compression. Tumor debulking and laminectomy were performed emergently. The tumor consisted of noncohesive blast cells. The CBC revealed a leukocyte count of 238,300/microl and a differential consistent with CML. Reexamination of the patient found that the abdominal mass was a giant spleen. Further immunohistochemical studies of the tumor were consistent with extramedullary acute megakaryoblastic blast transformation of CML. Although extramedullary blast crises herald the accelerated phases in approximately 10% of CML cases, megakaryoblastic blast transformation of CML accounts for less than 3% of these cases. The combination of acute paraplegia and megakaryoblastic transformation in a previously undiagnosed patient with CML is extremely rare and may pose a diagnostic dilemma.

Chronic myeloid leukemia: pathophysiology, diagnostic parameters, and current treatment concepts

Chronic myeloid leukemia (CML) is a stem cell disease characterized by excessive accumulation of clonal myeloid (precursor) cells in hematopoietic tissues. CML cells display the translocation t(9; 22) that creates the bcr/abl oncogene. The respective oncoprotein (= BCR/ABL) exhibits constitutive tyrosine kinase activity and promotes growth and survival in CML cells. Clinically, CML can be divided into three phases: the chronic phase (CP), the accelerated phase (AP), and the blast phase (BP) that resembles acute leukemia. Progression to AP and BP is associated with occurrence of additional genetic defects that cooperate with bcr/abl in leukemogenesis and lead to resistance against antileukemic drugs. The prognosis in CML is variable depending on the phase of disease, age, and response to therapy. The only curative approach available to date is stem cell transplantation. For those who cannot be transplanted, the BCR/ABL tyrosine kinase inhibitor STI571 (Glivec, Imatinib), interferon-alpha (with or without ARAC), or other cytoreductive drugs are prescribed. Currently available data show that STI571 is a superior compound compared to other drugs in producing complete cytogenetic and molecular responses. However, despite superior initial data and high expectations for an effect on survival, long term results are not available so far, and resistance against STI571 has been reported. Forthcoming strategies are therefore attempting to prevent or counteract STI571 resistance by co-administration of other antileukemic drugs. Whether these strategies will lead to curative drug therapy in CML in the future remains at present unknown.

Double Ph-positive megakaryoblastic transformation of chronic myeloid leukemia

A 64-yr-old Japanese man presented with mild anemia, leukocytosis, and thrombocytosis in November 1999. A diagnosis of chronic myeloid leukemia was made with a positive Ph chromosome, and interferon alpha treatment was started, 6 million units a day. Two years later, in October 2001, the patient developed leukocytosis, an increased LDH level, and large blasts with basophilic cytoplasm with cytoplasmic projections appeared in the peripheral blood. Bone marrow aspiration revealed increased blasts (59.6%). These blasts were negative on peroxidase stain, positive on acid phosphatase, and weakly positive on alpha naphthyl butyrate esterase stain and periodic acid-Schiff stain. Immunohistochemical staining with monoclonal antibodies revealed that these blasts were strongly positive with anti-CD41 (glycoprotein IIb/IIIa), weakly positive with CD7, CD33, and CD34, and negative with other monoclonal antibodies. A diagnosis of megakaryoblastic transformation from chronic myeloid leukemia was therefore made. Two-color fluorescence in situ hybridization (FISH) for portions of the major-bcr and abl genes from bone marrow cells revealed two fused signals in 90.6% and one fused signal in 5.8% of 106 cells. A cytogenetic study revealed that bone marrow cells were 69, XYY, +6, -7, +8, -9, t(9;22)(q34;q11), +11, +13, -15, -16, dic(17;18)(p11;p11), -18, +19, +21, der(22)t(9;22) in six of nine examined cells. These findings confirmed that these megakaryoblasts originated from megakaryocytes of the chronic myeloid leukemia clone.

Peripheral blood findings in chronic myeloproliferative disorders

Chronic myeloproliferative disorders are now frequently detected on routine total blood count. A careful analysis of PB smears allows the diagnosis in many cases, and helps to classify most of them. The peripheral blood parameters may be of prognostic value, especially in AMM. During the follow-up of CMPD, modifications of the PB are of great interest to detect an evolution toward a myelofibrosis or a blastic phase.

CD56+ blastic transformation of chronic myeloid leukemia involving the skin

We report on two patients with chronic myeloid leukemia (CML) who presented blastic transformation involving the skin, with leukemic infiltrates showing unusual morphologic and immunohistologic characteristics. Both patients were elderly men with a 36-month and a 40-month history of CML, respectively. They presented with disseminated, reddish to violaceous papules and plaques (case 1), and with localized reddish nodules on the left temporal area (case 2). Concurrent features of blastic transformation in the bone marrow were observed in one patient (case 1). Histopathologic examination of skin lesions revealed similar features in both cases. There was a moderate to dense dermal infiltrate composed mainly of medium-sized atypical mononuclear myeloid precursor cells with only few relatively well-differentiated cells of the granulocytic series. Histochemical staining for naphthol-ASD-chloroacetate esterase revealed strong positivity (>50% of neoplastic cells) in case 2 and only scattered positivity (< 10% of neoplastic cells) in case 1. Immunohistologic analysis performed on paraffin-embedded sections showed in both cases variable reactivity of neoplastic cells for leucocyte common antigen (CD45), lysozyme, myeloperoxidase, CD11c, CD15, CD43, CD66, CD68, HLA-DR, and the neural cell adhesion molecule (NCAM) CD56. A negative reaction was observed for CD3, CD34, and TdT. The immunohistologic findings were remarkably similar to those reported for acute myeloid leukemia (AML) with monocytic differentiation (French-American-British [FAB] classification, subtype M4). Examination of blasts from the bone marrow performed in one patient (case 1) revealed a similar phenotype also with CD56 expression. In conclusion, our observations show that specific cutaneous infiltrates in CML may show morphologic and immunohistochemical characteristics similar to those observed in AML with monocytic differentiation. Moreover, specific cutaneous manifestations of CML may express CD56.

CD7 expression on CD34+ cells from chronic myeloid leukaemia in chronic phase

Thirty-seven patients with chronic phase chronic myeloid leukaemia and fourteen healthy controls have been evaluated for lineage differentiation with immunological markers on purified bone marrow CD34 positive cells by multiparameter flow cytometry. The myeloid-associated antigen CD33 and the stem cell factor receptor (CD117, c-kit) was expressed by 82.3% and 73.5% on CP-CML patients and by 57% and 57.5% on healthy donors, respectively (P < 0.005). CD34+/CD19+ or CD34+/CD10+ B-lymphoid cell population represented 9. 1% and 10.7% of the CD34+ cells in CML whereas in normal controls this subpopulation was expressed by 27.9% and 30.4% of the CD34+ cells, respectively (P< 0.005). The T-lineage associated markers (CD7 and CD2) were detected on a minor population of CD34+ BM cells of healthy controls (mean, 3.6% and 4.6%, respectively). The CD2 positive cells represented 1.5% of the CD34+ cells in CML patients. CP-CML patients co-expressed the CD7 antigen on a mean of 32.6% of the CD34+ BM cells. Moreover, 93% of this CD34/CD7 double positive subpopulation co-expressed CD33 antigen in CML patients. Co-expression of CD7 on CD34+ cells was induced to decrease significantly after short-term in vitro culture with the differentiation-inducing agent phorbol ester (PMA) and with a combination of cytokines (stem-cell factor, interleukin-3 and granulocyte colony-stimulating factor). In conclusion, a high co-expression of CD7 antigen is demonstrated on CD34+ cells of chronic phase-chronic myeloid leukaemia patients. The loss of CD7 marker following incubation with PMA and cytokines suggests that this antigen is expressed transiently in early myeloid leukaemic CML haemopoiesis.