New insights in the pathogenesis of T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) represent diverse and aggressive malignancies, with few recent therapeutic improvements. Recent high-throughput genomic studies have revealed the complex mutational landscape of these rare diseases. These novel findings provide the grounds to a more comprehensive classification of these diseases, reflected in the 2017 WHO classification.

Our review is focused on selected PTCL entities. Angioimmunoblastic T-cell lymphoma and other lymphomas derived from T follicular helper cells feature a rather homogeneous mutational landscape. These neoplasms recapitulate a multistep oncogenic process associating epigenetic deregulation, and second hit mutations affecting the T-cell receptor signaling pathway. This model inferred from comprehensive analyses of patients samples, was confirmed in mouse models. Among ALK-negative anaplastic large-cell lymphomas, translocation-associated subsets are found in both systemic and cutaneous types, and the newly described breast implant-associated type is usually indolent. Extranodal lymphomas of the innate immune system also harbor a combination of mutations affecting different classes of epigenetic modifiers, and mutation-induced activation of the Janus Kinase/signal transduction and activator of transcription pathway.

Understanding of PTCL pathogenesis has substantially improved, and oncogenic events have been identified. The current challenge is to mount efficient therapeutic strategies targeting these aberrations to improve patients' outcome.