Angioimmunoblastic T-cell lymphoma (AITL) is a rare and aggressive form of lymphoma that affects the immune system. It develops from T cells, a type of white blood cell that normally helps regulate the immune response. This type of lymphoma typically begins in the lymph nodes but can also affect other parts of the body, including the liver, spleen, bone marrow, and skin.
AITL is considered aggressive because it can grow and spread rapidly if left untreated. It is also associated with immune system dysfunction, which can cause symptoms and blood test abnormalities that are not usually seen in other types of lymphoma.
The symptoms of AITL are caused by both the cancer itself and the changes it triggers in the immune system. They may vary widely from person to person.
Common symptoms include:
Fever, night sweats, and unexplained weight loss (called “B symptoms”).
Enlarged lymph nodes, often in several parts of the body.
Swelling of the liver or spleen, which may cause abdominal discomfort or a feeling of fullness.
Skin rashes, which may appear as itchy or raised red spots.
Fluid buildup in the chest (pleural effusion) or abdomen (ascites), leading to shortness of breath or swelling.
Joint pain or arthritis.
Blood tests may reveal anemia (low red blood cell count), low platelet levels, or abnormal antibodies. These findings reflect immune dysregulation, a hallmark feature of this disease.
The exact cause of AITL is not fully understood, but research shows it develops when genetic mutations occur in T cells. These changes disrupt normal cell growth and function, allowing the cells to become cancerous.
The most common genetic changes include:
TET2 and DNMT3A mutations: Early changes that interfere with DNA regulation and allow abnormal cell behavior.
RHOA mutation: This mutation is observed in most cases, altering how cells send signals and driving the transformation into lymphoma.
IDH2 mutation: Found in some cases and linked to more aggressive disease.
Other mutations in genes such as VAV1, PLCG1, and CD28 promote uncontrolled growth but are less common.
In addition to these mutations, AITL is often associated with an immune system imbalance. Some patients exhibit signs of chronic immune stimulation, and in some instances, infections may contribute to this condition. These factors may act together to trigger the disease, although the precise cause remains unknown.
Diagnosing AITL requires a combination of medical evaluation, laboratory studies, and tissue examination.
Medical history and physical exam: Your doctor will look for symptoms such as swollen lymph nodes, skin changes, or signs of immune dysfunction.
Biopsy: A sample from a lymph node or other affected tissue is examined under the microscope.
Blood tests: These may reveal anemia, low platelet counts, or abnormal antibodies. In some cases, cancer cells can be detected in the blood using a test called flow cytometry.
Immunohistochemistry and genetic tests: Special tests help confirm the diagnosis and may identify genetic mutations.
Because AITL can mimic other conditions, a careful and thorough work-up is needed to reach the correct diagnosis.
When examined under the microscope, AITL often shows a mixture of cancerous T cells and other immune cells. The abnormal T cells may actually make up only a minority of the cells present, which can make the diagnosis challenging.
Typical features include:
Clusters of abnormal T cells replace the normal lymph node structure.
Small to medium-sized cancerous T cells with pale, clear cytoplasm and irregular nuclei.
A background of other immune cells, such as small lymphocytes, plasma cells, and histiocytes.
Prominent blood vessels in the lymph node, which may become enlarged and thick-walled in later stages.
AITL can resemble a reactive lymph node or even other types of lymphoma, such as EBV-positive diffuse large B-cell lymphoma or Hodgkin lymphoma. This is because the cancerous T cells often stimulate the growth of EBV-positive B cells and plasma cells.
Pathologists use several laboratory tests to confirm the diagnosis and separate AITL from other diseases.
This test highlights specific proteins in the cells. In AITL, the cancer cells:
Always express CD4, a marker of helper T cells.
Express follicular helper T-cell markers such as CD10, BCL6, PD1, ICOS, and CXCL13.
They often express general T-cell markers, such as CD2, CD3, and CD5, but may lose some markers, such as CD7.
These DNA-based tests check whether the T cells are all copies of one another (clonal) or a mixed population (polyclonal). A clonal pattern supports the diagnosis of lymphoma, but because the cancerous T cells may be a minority of the sample, false negatives are possible. Proof of clonality is helpful but not required to make the diagnosis.
Molecular tests can be used to detect mutations in genes such as RHOA, TET2, DNMT3A, or IDH2. These results may help researchers and guide clinical trials, but they do not yet routinely inform treatment decisions.
AITL has a variable prognosis. Some patients experience periods where the disease seems to regress, followed by sudden recurrences.
On average, approximately half of patients survive for three years after diagnosis, while some achieve long-term remission. The outlook often depends on age, overall health, and the stage of the disease at diagnosis.
Doctors sometimes use a scoring system called the Prognostic Index for Angioimmunoblastic T-cell Lymphoma (PIAI), which groups patients into low-, intermediate-, and high-risk categories based on clinical and laboratory features.
What features of my biopsy and tests support the diagnosis of AITL?
Has my blood or bone marrow been affected by this lymphoma?
Are genetic changes such as RHOA, TET2, or IDH2 present in my cancer cells, and what do they mean for me?
What stage is my disease, and how will that affect treatment?
What treatment options are available, and are there clinical trials I should consider?
How will we monitor my response to treatment?