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What Is Acute Lymphocytic Leukemia (ALL)?
Acute lymphocytic leukemia (ALL) is a cancer that starts in your bone marrow (the soft inner part of certain bones, where new blood cells are made).
You might also hear it called acute lymphoblastic leukemia.
With this type of leukemia, the cancer cells usually invade your blood fairly quickly. They can also sometimes spread to other parts of your body, including your lymph nodes, liver, spleen, central nervous system (brain and spinal cord), testicles (in males), and other organs.
What type of leukemia is ALL?
Leukemias are cancers that start in cells that would normally develop into different types of blood cells. Most often, leukemia starts in early forms of white blood cells, but some leukemias start in other blood cell types.
There are several types of leukemia. They are divided based mainly on whether the leukemia is acute (fast growing) or chronic (slower growing), and whether it starts in myeloid cells or lymphoid cells.
ALL is an acute (fast-growing) leukemia that starts in lymphoid cells.
Key facts about ALL
- ALL is an acute leukemia; it can progress quickly and usually needs to be treated right away.
- It is more common in children and teens than in adults.
- It starts in early (immature) forms of lymphocytes, a type of white blood cell.
There are 2 main types of ALL:
- B-cell ALL starts in early forms of B lymphocytes (B cells).
- T-cell ALL starts in early forms of T lymphocytes (T cells).
ALL can start in early B cells or T cells at different stages of maturity. This is discussed in Acute Lymphocytic Leukemia (ALL) Subtypes and Prognostic Factors.
What is the difference between lymphocytic leukemia and lymphoma?
ALL isn’t the only cancer that starts in the lymphocytes. Other types of cancer, such as lymphomas, also start in these cells. (This is true of non-Hodgkin lymphoma and Hodgkin lymphoma.)
The main difference between lymphocytic (lymphoblastic) leukemias like ALL and lymphomas:
- Leukemias mainly affect the bone marrow and blood.
- Lymphomas mainly affect the lymph nodes or other organs, although they may also involve the bone marrow.
But there is often some overlap.
Sometimes it can be hard to tell if a cancer of lymphocytes is a leukemia or a lymphoma. In fact, the World Health Organization considers ALL and lymphoblastic lymphoma (LBL) to be different versions of the same disease (ALL/LBL).
- Usually, if at least 20% of the bone marrow is made up of early forms lymphocytes (called lymphoblasts or just blasts), the disease is called ALL.
- If the disease is in other parts of the body with fewer blasts in the bone marrow, it is labeled as LBL.
Dig deeper
- Anatomy Gallery —Blood Cells and Bone Marrow (includes more about lymphocytes)
- How Do Blood Cells Mature and What Happens When They Don’t Form Normally
- Written by
- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
Alaggio R, Amador C, Anagnostopoulos I, et al. The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Lymphoid Neoplasms. Leukemia. 2022 Jul;36(7):1720-1748. Erratum in: Leukemia. 2023 Sep;37(9):1944-1951.
Appelbaum FR. Chapter 95: Acute Leukemias in Adults. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa. Elsevier: 2020.
National Cancer Institute. Acute Lymphoblastic Leukemia Treatment (PDQ®)–Patient Version. 2025. Accessed at https://www.cancer.gov/types/leukemia/patient/adult-all-treatment-pdq on May 5, 2025.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Acute Lymphoblastic Leukemia. Version 3.2024. Accessed at https://www.nccn.org on May 5, 2025.
Last Revised: August 13, 2025
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