← Back
Treatment and the treatment process

B-ALL and T-ALL: the difference

Acute lymphoblastic leukemia is divided into two main types: B-cell (B-ALL) and T-cell (T-ALL). This topic explains the difference in simple words.

Last updated: ~2 min read
On a dark navy background, a lymphoid stem cell splits into two branches: gold B cells and teal T cells.
Figure 1.B-ALL and T-ALL come from two different lymphocyte lines.

01Short answer

B-ALL and T-ALL arise from two different lines of lymphocytes. B-ALL is more common — about 75–85% of ALL — and starts from precursors of B lymphocytes, which mature in the bone marrow. T-ALL arises from precursors of T lymphocytes, which mature in the thymus; it is more common in teenagers and young men and may present with a high white cell count and a mass in the chest (mediastinum). The type is identified by flow cytometry from markers on the cell surface (CD19 and CD22 for B; CD3 and CD7 for T). Both are treated with combination chemotherapy, but immunotherapy (blinatumomab, inotuzumab, CAR-T) is mainly for B-ALL, while drugs such as nelarabine are used in T-ALL.

02Simple explanation

Two families. Lymphocytes form two "families": B cells make antibodies, T cells attack directly.

Where do they mature? B cells in the bone marrow, T cells in the thymus behind the breastbone.

How are they told apart? By "tags" on the cell surface.

Why does it matter? Parts of treatment are chosen by type.

03Scientific explanation

Immunophenotype: B-ALL carries CD19, CD22, CD79a and TdT; T-ALL carries cytoplasmic CD3, CD7 and other T markers (WHO, ACS).

Genetics: B-ALL can have BCR::ABL1 (Ph+), ETV6::RUNX1, hyperdiploidy, KMT2A rearrangements or Ph-like ALL; T-ALL often has NOTCH1 and other changes. Early T-precursor (ETP) ALL is a separate subgroup.

Treatment differences: CD19/CD22-targeted immunotherapy in B-ALL; tyrosine kinase inhibitors in Ph+ B-ALL; nelarabine at relapse in T-ALL, and more intensive CNS prevention in some protocols.

04What happens in the body?

Differences in symptoms

Both types can cause tiredness, bleeding and infections. In T-ALL, a mass in the chest can also cause breathlessness, cough or swelling of the face and neck.

A translucent chest silhouette with a glowing thymus area behind the breastbone.
Figure 2.T-ALL can cause a mass in the chest.

Differences in diagnosis

Flow cytometry identifies the type: a laser beam "reads" each cell and counts the markers on its surface. The result is usually ready within hours or a day.

Two translucent cells with gold and teal markers under a laser beam.
Figure 3.Markers on the cell surface show the type.

Differences in outlook

Results for B-ALL in children are very good; with modern treatment, results for T-ALL have also improved a lot. The outlook depends more on genetics and MRD response than on type.

05How is the type identified?

A simplified path.

Sample — Blood or bone marrow.1SampleBlood or bone marrow.
Flow cytometry — Surface markers.2Flow cytometrySurface markers.
Imaging — Chest X-ray if needed.3ImagingChest X-ray if needed.
Protocol — A plan matched to type.4ProtocolA plan matched to type.
B-ALLCD19, CD22.
T-ALLCD3, CD7.
PlanBy type.

06B-ALL and T-ALL compared

FeatureB-ALLT-ALL
FrequencyAbout 75–85%About 15–25%
OriginB precursors in the marrowT precursors in the thymus
Typical ageMore often childrenTeenagers and young men
Special sign—Chest mass
MarkersCD19, CD22, CD79aCD3, CD7
ImmunotherapyBlinatumomab, inotuzumab, CAR-TLimited; nelarabine

* Figures are approximate and vary by source.

07Key terms

B lymphocyte
An immune cell that makes antibodies.
T lymphocyte
An immune cell that attacks infected and changed cells.
Thymus
A gland behind the breastbone where T cells mature.
Mediastinum
The middle of the chest, between the lungs.
Immunophenotype
A cell’s set of surface markers.
ETP-ALL
Early T-precursor ALL subtype.

08Key points

  • ALL has two main types.
  • B-ALL is more common.
  • T-ALL can cause a chest mass.
  • Flow cytometry identifies the type.
  • Immunotherapy is mainly for B-ALL.
  • Genetics and MRD shape the outlook.

09Frequently asked questions

Which type is "better"?

There is no simple answer; the outcome depends on genetics, age and response to treatment.

Can B-ALL turn into T-ALL?

Usually not; the type does not change. A lineage switch at relapse has been described very rarely.

Is treatment completely different?

The core is similar; some drugs and protocols differ.

Is it the same in adults?

Yes, the same two types exist, but the genetic profile may differ.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Which type is "better"?

  2. Can B-ALL turn into T-ALL?

  3. Is treatment completely different?

  4. Is it the same in adults?

My questions

12Sources

  1. National Cancer Institute (NCI). Adult Acute Lymphoblastic Leukemia Treatment (PDQ)
  2. American Cancer Society. How Is Acute Lymphocytic Leukemia Classified?
  3. Cancer Research UK. Types of acute lymphoblastic leukaemia (ALL)
  4. Leukemia & Lymphoma Society. ALL subtypes
  5. WHO / IARC. WHO Classification of Haematolymphoid Tumours, 5th edition
  6. MedlinePlus. Acute lymphocytic leukemia (ALL)
  7. American Cancer Society. Targeted Therapy Drugs for Acute Myeloid Leukemia (AML)
  8. American Cancer Society. Targeted Therapy Drugs for Acute Lymphocytic Leukemia
  9. American Cancer Society. Targeted Therapy Drugs for CML
  10. American Cancer Society. Targeted Therapy Drugs for CLL
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
Last updated: ← Back to the list

Open the interactive site →