Angioimmunoblastic T-cell Lymphoma

TFH-derived peripheral T-cell lymphoma — RHOA G17V, TET2/DNMT3A mutations, immune dysregulation, and emerging targeted therapies

Key Points

• AITL is one of the most common peripheral T-cell lymphomas (PTCL), accounting for ~15–20% of all PTCL cases and arising from follicular helper T (TFH) cells.
• Hallmark mutations include RHOA G17V (~60–70%), TET2 (~80%), DNMT3A (~30%), and IDH2 R172 (~20–30%), with TET2 and DNMT3A often arising in hematopoietic stem cells.
• Clinical presentation is typically systemic: generalized lymphadenopathy, hepatosplenomegaly, B symptoms, skin rash, polyclonal hypergammaglobulinemia, and frequent autoimmune phenomena (hemolytic anemia, immune thrombocytopenia).
• EBV-positive B cells are detected in tumor tissue in the majority of cases, reflecting immune dysregulation; EBV-driven B-cell lymphoproliferation can occur as a secondary complication.
• Standard first-line therapy is CHOP or CHOP-like regimens; outcomes are poor with 5-year OS of ~30–35%. Consolidation with autologous stem cell transplantation is offered to eligible responders.
• Novel agents showing activity include romidepsin, belinostat (HDAC inhibitors), mogamulizumab (anti-CCR4), and IDH2 inhibitor enasidenib for IDH2-mutated disease.

Pathogenesis and Molecular Biology

AITL originates from follicular helper T cells (TFH), a CD4+ T-cell subset that normally resides in germinal centers and supports B-cell differentiation. Neoplastic TFH cells in AITL retain their immunophenotype (CD4+, CD10+, BCL6+, CXCL13+, PD-1+, ICOS+, SAP+), which is diagnostically helpful. The mutational landscape of AITL is distinctive. TET2 (a DNA demethylase) and DNMT3A (a DNA methyltransferase) mutations are detected in 70–80% and 20–30% of cases, respectively, and are thought to arise early in hematopoietic progenitors — predisposing cells to lymphomagenesis. RHOA G17V, a…

Clinical Features and Diagnosis

AITL presents with a distinctive clinical syndrome. Patients are typically middle-aged to elderly and present with stage III–IV disease at diagnosis in more than 80% of cases. Cardinal features include generalized lymphadenopathy, hepatosplenomegaly, and constitutional B symptoms (fever, night sweats, weight loss). Unique features that distinguish AITL from other lymphomas include: - Skin rash: a pruritic, maculopapular eruption occurring in up to 50% of patients, often triggered by amoxicillin - Polyclonal hypergammaglobulinemia: reflecting uncontrolled B-cell stimulation by neoplastic TFH…

Staging and Risk Stratification

AITL is staged using the Ann Arbor/Lugano classification, with PET-CT providing functional staging. The vast majority of patients present at advanced stage (III–IV). The Prognostic Index for T-cell Lymphoma (PIT) is the most validated prognostic tool for PTCL, including AITL. It incorporates age >60, ECOG performance status ≥2, LDH above normal, and bone marrow involvement. Patients with 0 risk factors have a 5-year OS of ~50%; those with 3–4 risk factors have a 5-year OS of approximately 10–15%. The International Peripheral T-cell Lymphoma Project showed that AITL has a relatively better…

Treatment

**First-Line Therapy** CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) every 21 days for 6–8 cycles remains the standard first-line regimen for AITL, though it produces complete remission rates of only ~40–50% and durable responses are uncommon. Some centers add etoposide to yield CHOEP, which may improve outcomes in younger patients, though data in AITL specifically are extrapolated from broader PTCL studies. For patients who respond to induction chemotherapy, consolidation with high-dose therapy and autologous stem cell transplantation (auto-SCT) is recommended for eligible…

Prognosis and Supportive Care

AITL carries a poor overall prognosis with standard therapy. Median OS with CHOP-based treatment is approximately 3 years, and 5-year OS is 30–35%. Many patients experience multiple relapses; transformation to a more aggressive lymphoma (including EBV+ DLBCL) can occur. Supportive care is integral given the systemic immune dysregulation. Autoimmune complications (hemolytic anemia, immune thrombocytopenia) may require corticosteroids or other immunosuppression. Hypogammaglobulinemia may develop after treatment and require IVIG supplementation. Opportunistic infections, including Pneumocystis…