What is Chronic Myelomonocytic Leukemia (CMML)?
Chronic myelomonocytic leukemia (CMML) is a type of hematologic malignancy that exhibits features of both myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPNs). It primarily affects the
bone marrow and blood, leading to an overproduction of monocytes and immature white blood cells. CMML is considered a clonal disorder of the hematopoietic stem cell, characterized by persistent monocytosis.
Histological Features of CMML
The histological examination of CMML typically involves the analysis of bone marrow biopsies and peripheral blood smears. Key findings include: Increased numbers of
monocytes in the peripheral blood.
Dysplastic changes in one or more of the myeloid cell lines.
Bone marrow hypercellularity with a predominance of granulocytic and monocytic cells.
Presence of
blast cells, although the percentage is usually less than 20%.
What Causes CMML?
The exact etiology of CMML is not fully understood, but it is believed to involve genetic mutations and environmental factors. Common genetic mutations associated with CMML include alterations in the
TET2,
ASXL1, and
SRSF2 genes. These mutations can lead to abnormal cell proliferation and differentiation.
Diagnosis of CMML
The diagnosis of CMML is based on a combination of clinical, hematological, and histological criteria. Key diagnostic steps include: Complete blood count (CBC) showing persistent monocytosis (monocyte count >1 x 10^9/L).
Bone marrow biopsy revealing hypercellularity and dysplasia.
Cytogenetic analysis to identify chromosomal abnormalities.
Molecular testing for specific gene mutations.
Histological Staining Techniques
Various staining techniques are employed to enhance the visualization of cells and structures in CMML. These include:
Prognostic Factors
Several factors affect the prognosis of CMML patients, including: Age and overall health of the patient.
Percentage of blast cells in the bone marrow and peripheral blood.
Specific genetic mutations and chromosomal abnormalities.
Clinical features such as anemia, thrombocytopenia, and organomegaly.
Histopathological Variants
CMML can be classified into two main subtypes based on the percentage of blast cells: CMML-1: Less than 5% blasts in the peripheral blood and less than 10% in the bone marrow.
CMML-2: 5-19% blasts in the peripheral blood and/or 10-19% in the bone marrow.
Treatment Options
The treatment of CMML often depends on the patient's age, overall health, and specific disease characteristics. Common treatment approaches include:
