New insights in the pathogenesis of T-cell lymphomas.

PURPOSE OF REVIEW: 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.

RECENT FINDINGS: 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.

SUMMARY: 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.