Angioimmunoblastic T-cell lymphoma (AITL) is a subtype of peripheral T-cell lymphoma derived from T-follicular helper cells. For pathologists, diagnosing AITL may be challenging due to its wide clinical and histopathologic spectrum, which can mimic a variety of reactive and neoplastic processes.
We summarize and discuss the clinicopathologic features of AITL, emphasizing diagnostic tools available to the practicing pathologist. Common diagnostic dilemmas are discussed.
AITL exhibits various histologic patterns and is often associated with a prominent microenvironment that can obscure the neoplastic cells. Atypical B-cell proliferations, which can take a number of forms, are common in AITL, and clonal B-cell expansion can be seen. The atypical B cells can closely resemble Hodgkin/Reed-Sternberg cells, leading to misdiagnosis as classic Hodgkin lymphoma. Molecular studies have revealed recurrent genetic alterations, which can aid in differential diagnosis, particularly in problematic cases.
Given the complex diagnostic challenges in AITL, an integrated approach, incorporating clinical, morphologic, immunophenotypic, and molecular findings, is helpful to reach an accurate diagnosis.

© American Society for Clinical Pathology, 2021.