Importance of CD117 in the Assignation of a Myeloid Lineage in Acute Leukemias.

The correct classification of acute leukemias (AL) is an essential part in the evaluation of any patient with this disease. Historically, CD117 has been an important asset in the diagnosis of patients with mixed-phenotype acute leukemia (MPAL). In an attempt to simplify the diagnosis of MPAL with fewer and more lineage specific markers, the World Health Organization (WHO) proposed in 2008 a new criteria for the diagnosis of this type of AL, which excluded CD117 from the myeloid markers that are utilized to diagnose MPAL. In order to assess whether CD117 is necessary in the diagnosis of MPAL, we evaluated the sensitivity and specificity of CD117 for acute myeloid leukemia (AML) in 331 patients with AL. The calculated sensitivity of CD117 for AML was 85.88% (103/120), while the specificity was 83.9% (177/211). Besides myeloperoxidase (MPO), which was used as the gold standard in differentiating AML from other type of ALs, the most specific markers for AML in our study were CD14 and CD64 (99.5 and 95.6%). Although the specificity of CD117 in this study is not as high as CD14 and CD64, markers concomitantly used in this this study and in the WHO classification, based on the results of other researches (i.e. the specificity of CD117 for AML was 100% in one study) and due to the fact that its specificity for AML in this study is relatively high, we recommend the use CD117 in assigning a myeloid lineage in MPAL.

[Myelodysplastic syndrome classification]. / La classification des syndromes myélodysplasiques.

Myelodysplastic syndromes (MDS) are myeloid disorders with various clinical and biological presentations. The French-American-British (FAB-1982) classification included five categories basing on morphology and bone marrow blast count. Three criteria are taken into account: 1) the percentage of blasts in peripheral blood and bone marrow, 2) the percentage of ringed sideroblasts, and 3) the number of monocytes in peripheral blood. The World Health Organization classification (WHO 2001, 2008) modifies the FAB system by also taking cytogenetic characteristics and molecular biology into consideration. The last classification (WHO-2008) takes into account: 1) the number of peripheral cytopenia, 2) the percentage of blasts in peripheral blood and bone marrow, 3) the percentage of ringed sideroblasts, 4) the possible presence of Auer Rods, and 5) the detection of a cytogenetic abnormality (the isolated 5q deletion). The following subgroups are defined: refractory cytopenia with unilineage dysplasia, refractory anemia with ringed sideroblasts, refractory cytopenia with multilineage dysplasia, refractory anemia with excess blasts, myelodysplastic syndrome unclassifiable and myelodysplastic syndrome with isolated del(5q).

Acute Myeloid Leukemia With Myelodysplasia-Related Changes: A New Definition.

Acute myeloid leukemia (AML) with multilineage dysplasia was introduced in the 2001 World Health Organization (WHO) classification to encompass cases of AML characterized by myelodysplastic syndrome-like features. The 2008 WHO classification revised this group into a new category, AML with myelodysplasia-related changes (AML-MRC). The category now includes patients with at least 20% blasts in peripheral blood or bone marrow and any of the following: (1) AML arising from a previous MDS or mixed MDS/myeloproliferative neoplasm, (2) AML with a specific MDS-associated cytogenetic abnormality and/or (3) AML with multilineage dysplasia. Up to 48% of all patients with AML are encompassed within the AML-MRC subgroup. AML-MRC patients have worse prognosis compared with patients with AML, not otherwise specified.

A Study of Mixed Phenotype Acute Leukemia Based on the 2008 World Health Organization Classification / 대한진단검사의학회지

BACKGROUND: We evaluated the clinical significance of revised 2008 WHO classification needed to diagnose mixed phenotype acute leukemia (MPAL). METHODS: A total of 22 MPAL patients, previously diagnosed by applying the scoring system of the European Group for Immunological Classification of Acute Leukemias (EGIL) were reclassified based on the 2008 WHO classification. RESULTS: In 2008 WHO classification, the number of monoclonal antibodies (mAbs) required for assigning more than one lineage was markedly decreased, from 26 to 11, compared with that of EGIL. Seventeen of the 22 MPAL patients were reclassified as MPAL with following details: 6 MPAL with t(9;22)(q34;q11.2); BCR-ABL1, 1 MPAL with t(v;11q23); MLL rearranged, 7 MPAL, B/Myeloid, not otherwise specified (NOS) and 3 MPAL, T/Myeloid, NOS. Five patients were excluded from MPAL in the revised classification: 4 cytoplasmic myeloperoxidase (cMPO)-negative and 1 CD19-negative. The failure of complete remission achievement and occurrence of relapse were associated with poor prognosis (P=0.0002 and P=0.009, respectively). But the presence of Philadelphia chromsome was not significantly related with patient outcome (P=0.082). One patient with cCD79a, CD20, CD38, cMPO and CD15, whose diagnosis was reclassified from MPAL to AML has survived during the study period. CONCLUSIONS: Because of decreased number of mAbs needed, it is possible that acute leukemia panel is designed to include all mAbs required to diagnose MPAL according to 2008 WHO classification. When diagnosing MPAL, it is critical to figure out positivity in either cMPO or CD19, and AML expressing more than 2 lymphoid antigens are considered as MPAL.