Myeloid neoplasms are a diverse group of cancers originating in the bone marrow, affecting the production of blood cells derived from myeloid stem cells. The defining feature is the uncontrolled growth or abnormal development of these myeloid cells, disrupting normal blood cell formation. These are considered hematologic malignancies, or cancers of the blood.
What Are Myeloid Neoplasms
The bone marrow is the primary site for hematopoiesis, the process of creating all blood cells. All blood cells originate from hematopoietic stem cells (HSCs), which reside in the bone marrow and can self-replicate and differentiate into various cell types. These HSCs can develop into either lymphoid stem cells or myeloid stem cells. Myeloid stem cells are the precursors to red blood cells, platelets, and most types of white blood cells, including granulocytes and monocytes.
In myeloid neoplasms, genetic mutations occur in these myeloid stem cells or early progenitor cells, leading to their abnormal proliferation and maturation. This results in the production of dysfunctional cells that either do not mature properly or are produced in excessive numbers. The accumulation of these abnormal cells can crowd out healthy blood-forming cells in the bone marrow, impairing the bone marrow’s ability to produce sufficient healthy red blood cells, white blood cells, and platelets.
Categories of Myeloid Neoplasms
Myeloid neoplasms are broadly categorized into several main types, each with distinct characteristics and behaviors. The World Health Organization (WHO) classification system is generally used to categorize these diseases.
Acute Myeloid Leukemia (AML)
Acute Myeloid Leukemia (AML) is an aggressive cancer characterized by the rapid proliferation and accumulation of immature myeloid cells, known as blasts, in the bone marrow and peripheral blood. These blasts are unable to mature into functional blood cells, leading to a severe deficiency of healthy red blood cells, white blood cells, and platelets. AML progresses quickly, often requiring immediate treatment.
Myelodysplastic Syndromes (MDS)
Myelodysplastic Syndromes (MDS) encompass a group of disorders where the bone marrow produces blood cells that are abnormal or immature and do not mature correctly. This ineffective blood cell production often leads to low blood cell counts, such as anemia, neutropenia, or thrombocytopenia. While MDS can be a chronic condition, there is a risk that it may transform into AML over time.
Myeloproliferative Neoplasms (MPN)
Myeloproliferative Neoplasms (MPN) involve the overproduction of one or more types of mature blood cells in the bone marrow, typically resulting in elevated blood cell counts. Examples include Polycythemia Vera (PV), characterized by excessive red blood cell production, often linked to a JAK2 V617F mutation. Essential Thrombocythemia (ET) involves an overabundance of platelets, which can lead to clotting or bleeding issues. Myelofibrosis (MF) is another MPN where scar tissue builds up in the bone marrow, impairing blood cell production and often causing an enlarged spleen. MPNs can also progress over time, sometimes leading to acute myeloid leukemia.
Recognizing Myeloid Neoplasms
Recognizing myeloid neoplasms often involves observing symptoms that arise from the bone marrow’s impaired ability to produce healthy blood cells. Individuals may experience fatigue and shortness of breath, indicating anemia from a low red blood cell count. Easy bruising or bleeding can point to a low platelet count. Recurring infections or fevers may occur due to an insufficient number of functional white blood cells.
Other general symptoms can include unexplained weight loss, night sweats, or a feeling of fullness due to an enlarged spleen or liver. If these symptoms are present, a healthcare provider will typically initiate a diagnostic process, beginning with a physical examination and a complete blood count (CBC). Abnormal results often prompt further investigation, such as a bone marrow biopsy and aspiration to collect a sample for microscopic examination. Genetic testing of the bone marrow sample is also commonly performed to identify specific mutations or chromosomal changes characteristic of different myeloid neoplasms.
Treatment Approaches for Myeloid Neoplasms
Treatment strategies for myeloid neoplasms are varied and depend significantly on the specific type of neoplasm, its stage, and the patient’s overall health. For acute myeloid leukemia (AML), chemotherapy is a primary treatment, using powerful drugs to destroy rapidly dividing cancer cells throughout the body.
Targeted therapy represents a more precise approach, utilizing drugs that specifically identify and attack cancer cells based on their genetic mutations or protein expressions. Stem cell transplantation involves replacing diseased bone marrow with healthy blood-forming stem cells, usually from a donor.
Supportive care measures are also an important part of managing myeloid neoplasms. These can include blood transfusions to address anemia or low platelet counts, and growth factors that stimulate the production of certain blood cells. Preventing and treating infections is also a focus. For some slow-growing or early-stage myelodysplastic syndromes (MDS) or myeloproliferative neoplasms (MPN), a “watch and wait” approach may be adopted. Clinical trials offer patients access to innovative and experimental therapies.