Test ID: MYEFL    
Myelodysplastic Syndrome by Flow Cytometry, Bone Marrow

Detecting increased blasts

Characterizing blast phenotypes

Identifying abnormal patterns of myeloid maturation as seen in myelodysplastic syndromes and other clonal myeloid neoplasms

Providing additional adjunct diagnostic information in cases with equivocal or suspicious morphologic features for myelodysplastic syndrome (MDS), MDS/myeloproliferative neoplasms including chronic myelomonocytic leukemia, and other clonal myeloid neoplasms

This assay uses 2 panels for identifying cell populations of interest and for characterizing their phenotypic features. In the myelodysplastic syndrome panel, blasts are identified by CD45/side scatter gating strategy and by CD34 expression; promyelocytes are identified by bright CD13, CD33, and CD117 expression without CD34; granulocytes and precursors are defined by their variable expression of CD13 and CD16 according to their maturational stages. Abnormal patterns of myeloid maturation are determined according to the presence or absence of the following features: distinct blast increases over 5%; heterogeneous blast distribution on CD13/HLA-DR plot; expression of CD2, CD7, and/or CD56 on blasts; and disrupted granulocytic maturation on CD13/CD16 plot.(1,2)

Additionally, a triage panel is performed to ensure that monotypic B-cells, increased plasma cells, and phenotypically aberrant populations of CD3-positive T-cells and CD16-positive/CD3-negative natural killer (NK) cells, if present, are identified. This is necessary especially for cases where the reason for referral is broad, where clonal myeloid neoplasms may not be the only diagnostic consideration, or where there is incomplete clinical history and morphologic data.

These panels are used in combination with any available provided clinical history and morphologic findings to determine if any additional testing may be needed for complete disease characterization. If such additional testing is required, it will be added according to laboratory algorithms at an additional charge per unique antibody tested.

Myelodysplastic syndromes (MDS) encompass a heterogeneous group of clonal hematopoietic neoplasms characterized by cytopenias due to ineffective hematopoiesis, variable degrees of dysmyelopoietic morphologic features, and increased risks of evolution to acute myeloid leukemia. Per 2008 World Health Organization recommendations, a definitive diagnosis of MDS requires identification of 1 or more of the following findings: clear-cut morphologic features of dysplasia in greater than or equal to 10% of the cells in 1 or more of the 3 hematopoietic lineages; increased (but <20%) blood or marrow blasts with or without Auer rods; and well-characterized clonal cytogenetic abnormalities.(3-4) 

However, at present, in approximately 50% of MDS patients, no informative or diagnostic clonal cytogenetic abnormalities are identified. Not infrequently, morphologic review of the patient’s blood and marrow specimen is inconclusive. And yet it is important to distinguish MDS and other clonal myeloid neoplasms from other nonmalignant and nonneoplastic possibilities in the differential diagnosis such as medication effects or other toxic exposures, copper deficiency, infections, and left-shifted hematopoietic regeneration, among others.  

In such settings, when used in conjunction with appropriate clinical and morphologic findings, flow cytometry immunophenotyping analysis can provide additional diagnostic information to help distinguish an underlying clonal hematopoietic neoplasm from a reactive or secondary response.(2,5)

An interpretive report will be provided. This test will be processed as a laboratory consultation. An interpretation of the immunophenotypic findings and, if available, morphologic features will be provided by a board-certified hematopathologist for every case.

The final interpretation integrates 1) the quantity of blasts; 2) blast phenotype with respect to CD13/HLA-DR expression and/or abnormal coexpression of CD2, CD7, and/or CD56; and 3) myeloid maturation patterns based on CD13/CD16 plot. In combination, the total number of abnormalities detected and the distinctiveness of the abnormalities themselves help determine the likelihood of specimen involvement by a clonal myeloid neoplasm.

The results of this assay are not intended to be stand-alone and need to be correlated with the patient’s clinical history, findings from the primary morphologic review of blood and marrow slides, and other laboratory features including cytogenetic and molecular genetic results.

The quantity of blasts as identified and reported in this assay should not form the basis upon which the final diagnosis or subclassification of acute myeloid leukemia, myelodysplastic syndrome, myeloproliferative neoplasms, or myelodysplastic/myeloproliferative neoplasms is established. For that purpose, the percentage of blasts derived from a morphologic review of the primarily prepared blood and marrow slides is required; per 2008 World Health Organization guidelines (If unable to perform at the client site, order PATHC / Pathology Consultation).

This assay should not be used to monitor response to therapy.

1. Kussick SJ, Fromm JR, Rossini A, et al: Four-color flow cytometry shows strong concordance with bone marrow morphology and cytogenetics in the evaluation for myelodysplasia. Am J Clin Pathol 2005;124:170-181

2. Jevremovic D, Timm MM, Reichard KK, et al: Loss of blast heterogeneity in myelodysplastic syndrome and other chronic myeloid neoplasms. Am J Clin Pathol 2014;142:292-298

3. Brunning RD, Orazi A, Germing U, LeBeau MM: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Edited by SH Swerdlow, E Campo, NL Harris, et al. IARC Lyon, 2008, pp 88-107 

4. Cioc AM, Nguyen PL: Myelodysplastic syndromes. In Hematopathology. Edited by E Hsi. Elsevier Saunders. Philadelphia, 2012, pp 523-546

5. van de Loosdrecht AA, Westers TM: Cutting edge: flow cytometry in myelodysplastic syndromes. J Natl Compr Canc Netw 2013;11:892-902