Chronic myelomonocytic leukemia with antecedent refractory anemia with excess blasts: Further evidence for the arbitrary nature of current classification systems

How I investigate chronic myelomonocytic leukemia

The 2016 revised 4th edition of the World Health Organization classification of hematopoietic neoplasms updated the diagnostic criteria for chronic myelomonocytic leukemia (CMML). Persistent peripheral blood monocytosis of at least 1 × 10⁹ /L and a percentage of monocytes ≥10% of the circulating white blood cell count (WBC) are both prerequisite criteria for this diagnosis. CMML represents the prototype of "overlapping" myeloid neoplasms with concurrent myeloproliferative and myelodysplastic features. However, clinical presentation is heterogeneous, with cases showing prevailing "dysplastic" features and others a predominant "proliferative" phenotype. Accounting for this diversity, two variants of CMML are recognized: "dysplastic" CMML defined by WBC < 13 × 10⁹ /L and "proliferative" CMML with WBC ≥ 13 × 10⁹ /L often showing features mimicking a myeloproliferative neoplasm. Although not an official WHO category, the "oligomonocytic" variant of CMML is defined by relative monocytosis with an absolute monocyte count of 0.5-0.9 × 10⁹ /L. It can be considered a "pre-phase," as it frequently anticipates the development of an overt, classic CMML. In an attempt at improving disease prognostication, the blast count based grading system for CMML of the WHO 2008 Classification has been expanded in 2016 to include a new "CMML-0" category. Lastly, the large body of knowledge on the molecular events occurring in CMML has been used to assist diagnosis and assess prognosis. Despite the step forwards, diagnosis of CMML still remains one of exclusion as no clinical, pathologic or molecular findings are specific for this disease. The current review brings insight into the spectrum of CMML and provides practical advice to approach suspected cases of CMML.

Proposed diagnostic criteria for classical chronic myelomonocytic leukemia (CMML), CMML variants and pre-CMML conditions

Chronic myelomonocytic leukemia (CMML) is a myeloid neoplasm characterized by dysplasia, abnormal production and accumulation of monocytic cells and an elevated risk of transforming into acute leukemia. Over the past two decades, our knowledge about the pathogenesis and molecular mechanisms in CMML has increased substantially. In parallel, better diagnostic criteria and therapeutic strategies have been developed. However, many questions remain regarding prognostication and optimal therapy. In addition, there is a need to define potential pre-phases of CMML and special CMML variants, and to separate these entities from each other and from conditions mimicking CMML. To address these unmet needs, an international consensus group met in a Working Conference in August 2018 and discussed open questions and issues around CMML, its variants, and pre-CMML conditions. The outcomes of this meeting are summarized herein and include diag nostic criteria and a proposed classification of pre-CMML conditions as well as refined minimal diagnostic criteria for classical CMML and special CMML variants, including oligomonocytic CMML and CMML associated with systemic mastocytosis. Moreover, we propose diagnostic standards and tools to distinguish between 'normal', pre-CMML and CMML entities. These criteria and standards should facilitate diagnostic and prognostic evaluations in daily practice and clinical studies in applied hematology.

Management recommendations for chronic myelomonocytic leukemia: consensus statements from the SIE, SIES, GITMO groups

With the aim of reviewing critical concepts and producing recommendations for the management of chronic myelomonocytic leukemia, key questions were selected according to the criterion of clinical relevance. Recommendations were produced using a Delphi process and four consensus conferences involving a panel of experts appointed by the Italian Society of Hematology and affiliated societies. This report presents the final statements and recommendations, covering patient evaluation at diagnosis, diagnostic criteria, risk classification, first-line therapy, monitoring, second-line therapy and allogeneic stem cell transplantation. For the first-line therapy, the panel recommended that patients with myelodysplastic-type chronic myelomonocytic leukemia and less than 10% blasts in bone marrow should be managed with supportive therapy aimed at correcting cytopenias. In patients with myelodysplastic-type chronic myelomonocytic leukemia with a high number of blasts in bone marrow (≥ 10%), supportive therapy should be integrated with the use of 5-azacytidine. Patients with myeloproliferative-type chronic myelomonocytic leukemia with a low number of blasts (<10%) should be treated with cytoreductive therapy. Hydroxyurea is the drug of choice to control cell proliferation and to reduce organomegaly. Patients with myeloproliferative-type chronic myelomonocytic leukemia, and a high number of blasts should receive polychemotherapy. Both in myelodysplastic-type and myeloproliferative-type chronic myelomonocytic leukemia, allogeneic stem cell transplantation should be offered within clinical trials in selected patients.