T-ALL symptoms and tests

Because T-ALL develops fast, symptoms usually appear quite quickly.

The main signs and symptoms of T-ALL are caused by not having enough normal, healthy blood cells, because there are too many leukaemia cells in your bone marrow.

Some of the most common symptoms of T-ALL include:

• Unexplained tiredness (fatigue)
• Bruising and bleeding – This is caused by a low number of platelets in your blood (a low platelet count). You may notice that you are:
• bruising easily
  • bleeding from your gums or nose
  • bleeding from wounds, which is hard to stop
  • having black, tarry poos or poos that are streaked with red, because of bleeding in your gut
  • getting headaches, having difficulty speaking or having difficulty moving parts of the body.
    • Frequent infections
    • Weight loss
    • Pain in the bones or joints - due to too many blood cells being packed into areas in your body.
    • Lumps in your neck, armpits or groin where your lymph nodes have swollen.

Some people with T-ALL have leukaemia cells in their central nervous system. This means there are leukaemia cells that have got into the fluid around their brain and spinal cord, known as the cerebrospinal fluid, or CSF. This is slightly more common in T-ALL than B-cell ALL.

Having leukaemia cells in your CSF can cause symptoms in the brain, like headaches, dizziness, seizures, confusion and trouble with memory, being sick (vomiting) or eyesight problems.

For some people with T-ALL, leukaemia cells can build up and form a mass in the chest area. You might hear this called a “mediastinal mass”. This is quite common in T-ALL.

The masses of leukaemia cells can lead to a build-up of fluid in the space around your lungs and heart.

In some cases, this fluid can press on a large vein that carries blood back to your heart, called the “superior vena cava”. This can cause:

• breathlessness
• swelling of your face and neck

It may feel worrying to be told this is happening. However, urgent treatment to treat the T-ALL will aim to get rid of the excess leukaemia cells that are causing the build-up of fluid and take the pressure off of your heart. This usually improves the symptoms that this is causing.

In some cases , the leukaemia cells in the body are found more as masses in the chest or other parts of the body, and less so in the bone marrow. If this is the case for you, you may hear your condition referred to as T-lymphoblastic lymphoma or T-LBL, but it won’t make a difference to your treatment plan.

Some people diagnosed with T-ALL have an extremely high number of white blood cells in their blood. This is called hyperleukocytosis. Having a very high number of white blood cells can affect how well blood flows around your body and lead to complications.
In some cases, people who have hyperleukocytosis need a treatment called leukapheresis. This removes some of the excess white blood cells in their blood. This might need to be done urgently as soon as you’re diagnosed.

Tumor lysis syndrome (TLS) is a serious medical condition in which a large number of cells die very quickly, releasing their contents into the blood. This can cause changes in the chemicals in your blood, and may lead to symptoms such as seizures, kidney problems, and heart issues.

You are more likely to develop TLS if you have a high number of leukemia cells in your blood and bone marrow. Your hospital team will aim to prevent you developing TLS by monitoring you closely and making sure you’re hydrated. Some people might also be given a drug called allopurinal to prevent TLS.

If you do develop TLS, you’ll be given lots of fluids to hydrate you and electrolytes to balance the chemicals in your blood. You may need other types of treatment and care to treat the TLS and help you recover.

Your doctor will need the results of a number of tests before you’re diagnosed with T-ALL. You will also have tests throughout your treatment, so your doctor can see how well your treatment is working.

You will also need different types of scans throughout diagnosis and treatment. This is also called 'imaging'.

Thank you to Professor Adele Fielding for supporting with the creation of this information and checking the clinical accuracy.

This information was first published in June 2026. Next full review due June 2029. We may make factual updates between reviews.