Everything You Need to Know About Blast Cells and Myeloblasts

How these cells are important for disease detection

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In biology and in medicine, the suffix "-blast" refers to immature cells known as precursor cells or stem cells. You can have blasts that give rise to all kinds of different specialized cells. For example, neuroblasts give rise to nerve cells and angioblasts give rise to fat cells. Just as nerve and fat cells develop from immature precursor cells, blood cells also come from immature blood-forming cells, or blasts, in the bone marrow.

Blood cells are continually formed to replace those that have become old or worn out. 

So, why is it important to know about blasts? In particular, bone marrow blast cells?

We all have blasts. In fact, we started out as a blast, a blastocyst to be exact – a jumble of cells that divided enough times to become an embryo. What is key to know is that the appearance of different types of blasts in unexpected areas of the body or the development of abnormal blasts can be an indicator of disease or cancer.

Bone Marrow Blast Cells 

In healthy bone marrow, blood-forming cells known as hematopoietic stem cells develop into red blood cells, white blood cells, and platelets through a process called hematopoiesis. This process occurs throughout your entire lifespan. The stem cell chooses its path of development into one of two cell lines, the lymphoid cell line or the myeloid cell line. In the myeloid cell line, the term "blast cell" refers to myeloblasts or myeloid blasts.

These are the very earliest and most immature cells of the myeloid cell line.

Although the cells of the myeloid cell line make up about 85 percent of the cells in bone marrow, less than 5 percent in the bone marrow should be blast cells. 

Myeloblasts give rise to white blood cells. This family of white blood cells includes neutrophils, eosinophils, basophils and monocytes, and macrophages.

The presence of these myeloblasts found circulating out in the bloodstream can be an important indicator of certain diseases such as acute myelogenous leukemia and myelodysplastic syndromes.

Myeloblast Disorders

In the case of acute myelogenous leukemia (AML) and myelodysplastic syndromes (MDS), there is an overproduction of abnormal myeloblasts. These cells are unable to develop further into mature white blood cells.

Acute myeloid leukemia is a type of cancer that goes by several other names, such as acute myelocytic leukemia, acute myelogenous leukemia, acute granulocytic leukemia, acute non-lymphocytic leukemia, or sometimes just AML. It is most common in older people. Most cases of AML develop from cells that would turn into white blood cells other than lymphocytes, however, some cases of AML develop in other types of blood-forming cells.

Myelodysplastic syndrome is a group of disorders that affects the production of new blood cells in the bone marrow. In these diseases, the bone marrow produces abnormal blast cells that fail to mature properly and are unable to function.

These abnormal blasts begin to take over the bone marrow and prevent the production of adequate numbers of other types of blood cells, such as platelets, red blood cells, and healthy white blood cells.

In fact, production of leukemic blasts may get so out of hand that the immature cells spill out from the bone marrow into the circulation. The presence of blast cells on a complete blood count (CBC) is therefore very suspicious for leukemia. Blast cells are not typically found in the circulating blood of healthy individuals.

Sources:

American Cancer Society. How Is Acute Myeloid Leukemia Classified? February 22, 2016.

Larson RA, Le Beau MM. Prognosis and Therapy When Acute Promyelocytic Leukemia and Other “Good Risk” Acute Myeloid Leukemias Occur as a Therapy-Related Myeloid Neoplasm. Mediterranean Journal of Hematology and Infectious Diseases. 2011;3(1):e2011032.

Zahid MF, Parnes A, Savani BN, Litzow MR, Hashmi SK. Therapy-related myeloid neoplasms - what have we learned so far? World Journal of Stem Cells. 2016;8(8):231-242.

"Comprehensive Review of Hematopoiesis and Immunology: Implications for Hematopoietic Stem Cell Transplant Recipients" in Ezzone, S. (2004) Hematopoietic Stem Cell Transplantation: A Manual for Nursing Practice Oncology Nursing Society: Pittsburgh, PA (pp.1- 12).

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