Angioimmunoblastic T cell lymphoma C84.4

Angioimmunoblastic T-cell lymphoma (AITL) is likely to be a peripheral low-grade malignant T-cell lymphoma with abnormal immune activity as one of its main features. Although AITL is now understood to be a neoplastic disease, it was early recognized to be an inflammatory overlying neoplastic disease (Chiba S et al. 2020), characterized by fever, generalized lymph node swelling, hepato-splenomegaly, hemolytic anemia, blood eosinophilia, and polyclonal dysglobulinemia.

Initially, an abnormal, non-neoplastic immune reaction (former names: angioimmunoblastic lymphadenopathy; lymphogranulomatosis X) was assumed due to e.g. drug- or viral-induced stimulation of the immune system. Clonal proliferation of T lymphocytes in the lymph nodes of patients with angioimmunoblastic lymphadenopathy (AILD) has been demonstrated in at least some of the patients. Some authors have suggested a continuum between cutaneous pseudolymphoma and cutaneous T-cell lymphoma.

The peak age is 60 years

90% of patients suffer from massive B-symptomatology. Fever, night sweats, fall subsidence, "pseudo-inflammatory" generalized lymph node swelling, hepato-, splenomegaly, hemolytic anemia.

Skin symptoms are observed in up to 50% of patients (Botros N et al 2015). They may appear as the first symptoms of peripheral T-cell lymphoma.

The skin manifestations are not very characteristic and develop in episodes. Generalized pruritus, erythema, maculopapular exanthema (drug-like), occasionally under the picture of DRESS syndrome (Mangana Jet al. 2017), and circumscribed lymphoma-specific nodules or plaques, sometimes reminiscent of mycosis fungoides.

In rare cases, associations with linear IgA dermatosis have been described (Colmant C et al 2020).

Infiltrates of small to medium-sized atypical T cells in front of a variably composed inflammatory polymorphic background of histiocytes, plasma cells, and eosinophilic granulocytes. The infiltrate cells are characteristically located between proliferated branched venules and follicular dendritic reticulum (FD) cells.

Infiltration of the perinodal soft tissue with recess of the marginal sinus is frequently found.

Characteristically, EBV-positive B immunoblasts are located in variable density in the paracortex. Reed- Sternberg-like cells (often EBV-positive) may also be present, mimicking classic Hodgkin's lymphoma here. EBV-positive B-immunoblasts can also become very prominent in the course - probably triggered by cytokines of the neoplastic FTH cells - and even progress to EBVpositive diffuse large B-cell lymphoma (DLBCL).

Immunophenotypically, neoplastic T cells predominantly express CD4 and TFH cell markers such as CD10, ICOS, BCL6, PD-1, and CXCL13 to a variable extent, in addition to pan-T antigens(CD2, CD3, CD5). CXCL13 is considered a potent molecular mediator affecting germinal center B-cell recruitment and B-cell activation and thus could promote B-cell expansion, plasmacytic differentiation and hypergammaglobulinemia.

Genetically , a clonal T-cell receptor gene arrangement can be detected in 70-90% of AITL cases, and a clonal immunoglobulin gene arrangement can also be detected in 25-30% of cases, attributable to EBV+ B blast expansion. Gene expression analyses show a distinct gene signature corresponding to the TFH cell with high expression of B and FD cell-associated genes, chemokines, chemokine receptors, and genes related to extracellular matrix and vascular biology. At the DNA level, an inactivating mutation of the small GTPase RHOA (p.Gly- 17Val) is detectable in 60-70%.

Furthermore, mutations are found in the epigenetic modifier genes IDH2, TET2 and DNMT3A . CTLA4-/CD28 gene fusion is detectable in 50%.

Drug reactions; viral exanthema; adult Still's syndrome; mycosis fungoides; T-cell lymphomas of other provenance (in particular, the distinction from peripheral T-cell lymphomas, not otherwise specified may be shcweirg. S. there).

Currently, there is no uniform therapeutic approach. For palliation of the usually pronounced B-symptomatology, 80-100 mg/day prednisolone (e.g. Decortin H) p.o. initially, descending dosage up to a maintenance therapy of 10-15 mg/day, non-steroidal anti-inflammatory drugs with or without oral alkylating agents (chlorambucil, cyclophosphamide) as well as T-cell immunosuppressants (cyclosporine) are recommended.

In case of insufficient response, polychemotherapy according to CHOP regimen, BLAM regimen or COP regimen; see also below Cytostatics. Improvement of the response rate through the addition of interferon alfa (e.g. Intron A, Roferon A).

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