Blast Cells and Myeloblasts Overview

High cell counts may be an indication of disease

Photomicrograph of human red bone marrow where eosinophils (red granular), neutrophils, and neuroblasts (blasts) are formed

Ed Reschke / Getty Images

Blast cells are immature cells known as precursor or stem cells. Blasts give rise to all kinds of different specialized cells. For example, neuroblasts give rise to nerve cells. Myeloblasts are immature white blood cells that develop in the bone marrow.

We all have blasts. In fact, each of us started out as a blast or, more precisely, a blastocyst (a jumble of cells that divides enough times to become an embryo). When different types of blasts appear in unexpected places, however, or when abnormal blasts develop, they can be an indicator of cancer or another disease.

This article discusses blasts and myeloblasts, how they form, and the conditions that affect them.

Photomicrograph of human red bone marrow where eosinophils (red granular), neutrophils, and neuroblasts (blasts) are formed

Ed Reschke / Getty Images

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 life span, as blood cells are continually formed to replace those that have become old or worn out. The stem cell chooses its path of development into one of two cell lines, lymphoid or myeloid.

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.

Myeloblasts give rise to white blood cells. This family of white blood cells includes:

Myeloblasts aren't typically found in the circulating blood of healthy people. When they are found in the blood, they can be an important indicator of such diseases as acute myelogenous leukemia and myelodysplastic syndromes.

Although the myeloid cell line accounts for about 85% of the cells in bone marrow, less than 5% should be composed of blast cells. Anything more may be an indication of a serious disease.

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 Myelogenous Leukemia

AML is a type of cancer that goes by several other names, such as acute myelocytic leukemia, acute myelogenous leukemia, acute granulocytic leukemia, or acute non-lymphocytic leukemia. It is most common in people who are older.

AML happens when blasts don't mature and build up in your bone marrow. When the production of these blasts gets out of hand, they can spill from the bone marrow into circulating blood. Their presence on a complete blood count (CBC) test is very suspicious for leukemia.

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 Syndromes

MDS is a group of cancers that affect 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.

MDS progresses to AML in about 1 in 3 people. Treatments like bone marrow transplant or certain medications can help slow or prevent this progression.

When to See a Healthcare Provider

While the symptoms of AML and MDS are often nonspecific in the early stages, you should see a doctor if you experience:

  • Prolonged bleeding
  • Easy bruising
  • Persistent fatigue
  • Frequent infection
  • Unexplained weight loss of 5% or more


Blasts are immature cells. It is normal to have blasts, but when they appear in places they aren't normally found, it can be a sign of disease.

Blasts in the blood are associated with cancers such as myelodysplastic syndromes and acute myelogenous leukemia. These conditions occur when immature blasts build up in the bone marrow and spill into the blood stream. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institutes of Health. Hematopoietic stem cells.

  2. American Cancer Society. Tests for acute myeloid leukemia (AML).

  3. Duong VH, Padron E, Al ali NH, et al. The prognostic value of circulating myeloblasts in patients with myelodysplastic syndromes. Ann Hematol. 2018;97(2):247-254.doi: 10.1007/s00277-017-3186-4

  4. Adult PDQ Adult Treatment Editorial Board. Adult acute myeloid leukemia treatment: patient version. In: PDQ Cancer Information Summaries. 2022.

  5. National Institutes of Health. Myelodysplastic syndromes.

  6. American Cancer Society. What are myelodysplastic syndromes?

Additional Reading

By Karen Raymaakers
Karen Raymaakers RN, CON(C) is a certified oncology nurse that has worked with leukemia and lymphoma patients for over a decade.