Whole-Genome Analysis and HLA Genotyping of Enteropathy-Type T-Cell Lymphoma Reveals 2 Distinct Lymphoma Subtypes

Background & Aims: Enteropathy-type T-cell lymphoma (ETL) is an aggressive extranodal T-cell non-Hodgkin lymphoma assumed to arise in the setting of celiac disease. Methods: To precisely define the genetic alterations underlying the pathogenesis of ETL, 30 ETL samples were profiled for genetic copy number alterations using high-resolution whole-genome tiling path array comparative genomic hybridization. To investigate the potential association of genetic alterations in ETL with celiac disease, HLA-DQB1 genotyping was performed. Results: By array comparative genomic hybridization, 13 novel recurrent minimal regions of chromosomal alteration were identified on multiple chromosome arms. ETL is characterized by frequent complex gains of 9q31.3-qter (70% of cases), or by an almost mutually exclusive 2.5-megabase loss of 16q12.1 (23% of cases). Two distinct groups of ETL could be delineated morphologically and genetically: type 1 ETL is characterized by nonmonomorphic cytomorphology, CD56 negativity, and chromosomal gains of 1q and 5q. Type 1 ETL also appears to be linked pathogenetically to celiac disease, sharing genetic alterations and HLA-DQB1 genotype patterns with (refractory) celiac disease. Type 2 ETL shows monomorphic small- to medium-sized tumor cell morphology, frequently shows CD56 expression, MYC oncogene locus gain, and rare gains of chromosomes 1q and 5q. In contrast to type 1 ETL, type 2 ETL shows a HLA-DQB1 genotype pattern more resembling that of the normal Caucasian population. Conclusions: Contrary to current clinical classification, ETL comprises 2 morphologically, clinically, and genetically distinct lymphoma entities. In addition, type 2 ETL may not be associated with celiac disease.