LabMed

Angioimmunoblastic T Cell Lymphoma (AITL)

At a Glance

Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma that usually occurs in older adults. Patients typically present with advanced stage lymphoma and are very ill at diagnosis. Lymph nodes are the main site of disease, but liver, spleen, skin, effusions, peripheral blood and bone marrow are commonly affected.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

AITL is usually diagnosed by a lymph node biopsy. Often, a core needle biopsy is not sufficient, and an excisional surgical biopsy is required. This diagnosis can sometimes be difficult to make, and patients often have multiple biopsies before a definitive diagnosis is reached. This lymphoma has a varied histologic appearance with polymorphous atypical lymphoid infiltrate, admixed with plasma cells, eosinophils, and histiocytes. There is a prominent vascular proliferation, expanded intrinsic cell network, and cortical expansion of B immunoblasts. The lymph nodes can be fibrotic and are sometimes described as looking "burned out."

Immunohistochemical staining demonstrates that the neoplastic T-cells are CD3+, CD4+, CD8-, CD10+, and CD30-. Dendritic markers like CD21 and CD23 highlight the abnormal expanded dendritic meshwork. Associated B immunoblasts stain for CD20, CD79a, and EBV (Epstein Barr Virus). These help differentiate AITL from other lymphomas and from reactive conditions.

Flow cytometry often identifies the abnormal T-cell population, which often coexpresses CD4 and CD10 (corresponding to the postulated origin from CD4+ follicular helper T-cells). Cytogenetic karyotype and fluorescence in situ hybridization (FISH) studies are usually not helpful. Molecular polymerase chain reaction (PCR) studies to look for T-cell receptor gene rearrangement can be very helpful and are usually clonal. IgH gene rearrangement, however, may also detect the clonal B-cell population corresponding to the expanded EBV+ B immunoblast population found in association with this T-cell lymphoma.

The diagnosis is made by positive tissue biopsy or cytopathologyvstudy of lymph node, bone marrow, or another involved site, with associated ancillary testing results, such as immunohistochemical staining, flow cytometry, and/or molecular PCR studies for T-cell receptor gene rearrangement.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

AITL can be difficult to diagnose, especially if only small biopsies are studied. It was formerly thought to be an atypical reactive condition that could progress to lymphoma (so-called angioimmunoblastic lymphadenitis), but now evidence shows that AITL is a de novo lymphoma.

AITL is almost always associated with EBV+ immunoblasts, although the actual lymphomatous T-cells are EBV negative. AITL can progress to or relapse as an EBV+ diffuse large B-cell lymphoma. Laboratory testing may also show polyclonal hypergammaglobulinemia, cold agglutinin, hemolysis, positive rheumatoid factor, and anti-smooth muscle cell antibodies.

What Lab Results Are Absolutely Confirmatory?

A confirmatory test is a positive tissue biopsy or cytopathology study.

What Factors, If Any, Might Affect the Confirmatory Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

AITL can be notoriously difficult to diagnose. Laboratory testing may also show EBV positivity, polyclonal hypergammaglobulinemia, cold agglutinin, hemolysis, positive rheumatoid factor, and anti-smooth muscle cell antibodies.

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