Angioimmunoblastic T-Cell Lymphoma (AITL) Is the Most Prevalent T-Cell Lymphoma Entity in Western Europe
Authors: Parrens Marie , Martin Antoine , Lamant Laurence , Delarue Richard , Haioun Corinne , Tournilhac Olivier , Berger Francoise , Bossard Céline , Bouchind'homme Brigitte , Briere Josette , Canioni Danielle , Charlotte Frederic , Fabiani Bettina , Molina Thierry Jo , Patey Martine , Petrella Tony , Picquenot Jean-Michel , Rousset Therese , Fataccioli Virginie , Delsol Georges , de Leval Laurence , Gaulard Philippe 
Published: October 2019

Abstract
Abstract 1607

Background:
Lymphoid malignancies derived from T and NK cells (PTCLs) constitute a heterogeneous group of uncommon disease entities, with marked geographic variation in their distribution. The most recent data from the International T-cell Lymphoma Project based on a retrospective analysis of PTCLs diagnosed between 1990 and 2002 (Blood. 2011;117(25): 6756–67) indicate that PTCL, not otherwise specified (PTCL,NOS) represents the most common PTCL worldwide (25,9%), followed by angioimmunoblastic T-cell lymphoma (AITL) (18,5%). Over the last few years, a better characterization of the cellular origin and pathophysiology of PTCLs has led to the development of new diagnostic markers.

Aim of the study:
To characterize the epidemiology of mature T/NK-cell malignancies in Western Europe (France and bordering countries) and to examine whether the availability of new tools/antibodies and changing concepts over the past years might have translated into an apparent change in the relative distribution of PTCL entities.

Materials and methods:
The histopathological diagnosis of PTCL entities according to the 2008 WHO classification were collected through two independent sets of PTCLs in France and bordering countries.

Results:
Over the past two years (2010–2011), 933 newly diagnosed non-cutaneous PTCLs were reviewed in reference centers through the prospective network “Lymphopath” aiming to review any newly diagnosed lymphoma in France. According to the 2008 WHO classification, the 933 PTCLs comprised: 314 AITL (33,6%), 239 PTCL,NOS (25,6%), 78 ALK-positive anaplastic large cell lymphoma (ALCL) (8,3%), 72 ALK-negative ALCL (7,7%), 59 extranodal NK/T-cell lymphomas (ENKTL 6%), 33 enteropathy-associated T-cell lymphoma (4%), 32 HTLV1+ adult T leukemia/lymphoma (3%), 7 hepatosplenic T-cell lymphoma (1%) and 99 cases of other entities or unclassifiable (11%).
A high prevalence of AITL was also found in an independent set of PTCLs retrospectively collected in the framework of a multicentric T-cell lymphoma research consortium “Tenomic” where non-cutaneous PTCL with frozen material available (n=623) from 1999 to 2009 in France and Belgium were retrieved and collegially reviewed for consensus diagnosis. In this collection, AITL (n=288, 46%) also outnumbered PTCL, NOS (n=215, 35%). Of the 196 AITL cases extensively investigated for CD10, TFH markers (PD1, CXCL13), CD21/CD23 follicular dendritic cells (FDC) and EBV, the initial diagnosis was recorded in 178 cases as: AITL in 155 cases (87%), PTCL, NOS in 21 cases (12%), and intermediate between PTCL,NOS and AITL (PTCL,NOS/AITL) in 2 cases, indicating the impact of additional stainings for the diagnosis of AITL. The 107 PTCL,NOS cases also extensively immunostained included 9 follicular variant of PTCL,NOS, 8 PTCL,NOS/AITL cases, 5 cases intermediate between PTCL,NOS and ALK-negative ALCL (of which 2 had been diagnosed as such and two as PTCL,NOS), and 85 remaining cases truly unspecified. Of these, 60 had been initially diagnosed as PTCL,NOS; 2 as PTCL,NOS/AITL; 4 as ALK-negative ALCLs and 1 as ENKTL.

Conclusion:
This study based on two independent large cohorts of non-cutaneous PTCLs highlights AITL as the most prevalent entity in Western Europe. It shows that extensive studies including investigation for CD10, TFH markers, FDC and EBV can at least partly contribute to the reclassification of some PTCL, NOS into the AITL spectrum category.

Disclosures:
No relevant conflicts of interest to declare.