Myeloperoxidase mRNA analysis in acute lymphoblastic leukemia

Mixed-Phenotype Acute Leukemia: Clinical Diagnosis and Therapeutic Strategies

Mixed-phenotype acute leukemia (MPAL) comprises a heterogenous group of leukemias that are genetically, immunophenotypically, and clinically, diverse. Given the rarity of the disease, the diagnosis and treatment of MPAL is extremely challenging. Recent collaborative efforts have made significant progress in understanding the complex genomic landscape of MPAL. Some retrospective studies support starting ALL-type induction followed by an allogeneic stem cell transplant(allo-sct) in the first complete remission; however, due to the inherent bias of retrospective data and small case series, a prospective validation of AML- and ALL-based regimen, and the incorporation of targeted therapies based on genetics and immunophenotype are warranted. The prognosis of adults and children with MPAL varies; this justifies modulating the intensity of therapy, including the use of allo-sct as a consolidation strategy.

Update on Acute Leukemias of Ambiguous Lineage

Acute leukemias of ambiguous lineage are a heterogenous group of diseases that include acute undifferentiated leukemias and mixed-phenotype acute leukemias (MPALs). These leukemias pose a challenge for pathologists and clinicians alike in diagnosis, treatment, and further management. Recent genetic characterization has provided insights into their underlying biology and classification, and has offered potential for targeted therapies. This article addresses diagnosis of MPALs with examples of the most common pitfalls, recent comprehensive molecular studies, and advancement in treatment and follow-up modalities.

Myeloid sarcoma of the head and neck region

CONTEXT

Myeloid sarcoma of the head and neck region can pose diagnostic challenges because of the low frequency of myeloid sarcoma and the potential for tumors of almost any lineage to occur in the head and neck.

OBJECTIVE

To study the clinicopathologic and immunohistochemical characteristics of myeloid sarcoma in the head and neck region and to review the differential diagnosis.

DESIGN

We searched for cases of myeloid sarcoma involving the head and neck region for a 24-year period at our institution. The medical records and pathology slides were reviewed. Additional immunohistochemical stains were performed.

RESULTS

We identified 17 patients, age 17 to 85 years. Most tumors involved the oral cavity. Myeloid sarcoma was the initial diagnosis in 9 patients (53%); the remaining 8 patients (47%) had a history of bone marrow disease. Immunohistochemical analysis using antibodies specific for lysozyme, CD43, and CD68 were highly sensitive for diagnosis but were not specific. By contrast, assessment for myeloperoxidase in this study was less sensitive but more specific. We also used antibodies specific for CD11c and CD33 in a subset of cases, and these reagents seem helpful as well.

CONCLUSIONS

The clinical presentation of myeloid sarcoma involving the head and neck, particularly the mouth, is often nonspecific, and a high degree of suspicion for the possibility of myeloid sarcoma is needed. Immunohistochemistry is very helpful for establishing the diagnosis.

Acute lymphoblastic leukemia with Burkitt-like morphologic features and high myeloperoxidase activity

Expression of a high level of myeloperoxidase (MPO) as a sole myeloid marker in acute leukemias that express typical lymphoblastic markers is unusual. Herein we report 5 cases of MPO+, otherwise typical acute lymphoblastic leukemia (ALL) without the expression of other myeloid markers. In most cases, MPO positivity was detected in more than 20% of blasts by immunologic (flow cytometric) and enzymatic testing. The striking feature of most of these cases is a morphologic picture reminiscent of that seen in Burkitt-like B-cell ALL with basophilic cytoplasm and vacuoles but no expression of surface immunoglobulin. All cases responded to ALL therapy and should be distinguished from myeloid leukemia and from Burkitt leukemia/lymphoma.

Myeloperoxidase immunoreactivity in adult acute lymphoblastic leukemia

To evaluate the frequency and significance of myeloperoxidase positivity in adult acute lymphoblastic leukemia (ALL), bone marrow biopsy material from 82 adults with ALL was evaluated with a polyclonal myeloperoxidase (pMPO) antibody. Nineteen cases (23%) demonstrated evidence of pMPO immunoreactivity. Positive cases were precursor B-cell lineage, and CD13 or CD15 expression was more frequent than in the pMPO-negative cases. A subset of pMPO-positive cases studied with a monoclonal MPO antibody was negative. Western blot analysis using the pMPO antibody showed the expected 55-kd band for myeloperoxidase in pMPO-positive and pMPO-negative ALLs, suggesting a lack of specificity of this antibody in ALL. Forty-two percent (8/19) of the pMPO-positive ALL cases demonstrated evidence of t(9;22) by either karyotype or polymerase chain reaction analysis. The pMPO-positive ALLs had a lower frequency of extramedullary disease than the pMPO-negative group and a trend toward improved overall survival compared with the pMPO-negative group. Immunoreactivity with pMPO in adult ALL may lead to an incorrect interpretation of biphenotypic acute leukemia using a recently described scoring system, and a revision to that scoring system is proposed to accommodate pMPO-positive ALL.

Diagnostic criteria for minimally differentiated acute myeloid leukemia (AML-M0). Evaluation and a proposal

We studied immunophenotypic features of 30 cases of minimally differentiated acute myeloid leukemia (AML-M0) using multiparameter flow cytometry and immunohistochemistry and evaluated the immunophenotypic features of previously reported cases to facilitate correct identification of myeloid lineage. All but 1 of our 30 cases expressed CD13 and/or CD33; 2 expressed CD19; 1 expressed CD10; none expressed both CD10 and CD19. Eleven of 30 cases expressed T-cell-associated antigens. All but 2 cases expressed CD34 and/or HLA-DR. Twelve of 27 cases expressed terminal deoxynucleotidyl transferase. Myeloperoxidase (MPO) expression was seen in 22 of 22 cases by immunohistochemistry and 1 of 4 by flow cytometry. None of 27 cases expressed cyCD3 and cyCD79a. We propose following modified criteria for AML-M0: (1) standard criteria for acute leukemia; (2) undetectable or less than 3% MPO or Sudan black B staining in blasts; (3) lack of expression of lymphoid-specific antigens, cyCD3 for T lineage and cyCD79 and cyCD22 for B lineage; and (4) positivity for any of the myelomonocytic lineage antigens known not to be expressed on normal T or B lymphocytes or positivity for MPO as detected by ultrastructural cytochemistry, immunohistochemistry, or flow cytometry.

Myeloperoxidase gene expression in non-infant pro-B acute lymphoblastic leukaemia with or without ALL1/AF4 transcript

In this study, we examined myeloperoxidase (MPO) gene expression in a series of 31 non-infant pro-B acute lymphoblastic leukaemia (ALL) patients that included 16 cases with the t(4;11) translocation and/or the resultant ALL1/AF4 chimaeric gene. Sixteen out of 31 cases (51%) were MPO mRNA positive/enzyme negative. MPO mRNA was detected in nine out of 16 (56%) and seven out of 15 (47%) patients with and without the ALL1/AF4 fusion transcript respectively. The comparative study between MPO mRNA positive and negative cases showed statistically significant differences with regard to age and white blood cell (WBC) count, and was 39.5 years vs. 26.3 years (P = 0.016) and 71.4 x 10(9)/l vs. 157.8 x 10(9)/l (P = 0.046) in the MPO mRNA positive and negative groups respectively. The correlation analysis between MPO mRNA expression, age, WBC count and leukaemic relapse according to the presence/absence of the ALL1/AF4 fusion showed that the statistically significant differences observed in the whole group were related mostly to the ALL1/AF4-positive ALL patients. In fact, in this latter group, the mean WBC count and patients' age were 85 +/- 79 x 10(9)/l vs. 289.8 +/- 102 x 10(9)/l (P = 0.0005) and 44.8 +/- 15.3 years vs. 26.7 +/- 13.7 years (P = 0.01) in patients with and without MPO mRNA expression respectively. It appears, therefore, that the assessment of MPO mRNA expression enables a further dissection of leukaemia heterogeneity in apparently homogeneous genetic/immunophenotypic ALL subsets.

AML-M0: a review of laboratory features and proposal of new diagnostic criteria

In 1991, the FAB group published a proposal to designate acute leukemias with minimal signs of myeloid differentiation as AML-M0. This proposal was meant to offer a provisional basis for the study of immature myeloid forms, with the understanding that it was susceptible to changes and improvements with new information derived from the laboratory. Since then there have been a number of reports detailing the biological and clinical features of patients with AML-M0. In this article we review the laboratory data acquired from various sources and suggest a partial modification of diagnostic criteria.