Peripheral T-Cell Lymphoma-NOS in Children and Adolescents: a Review from the Children's Oncology Group NHL Committee.

Peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS) is a rare mature T-cell non-Hodgkin lymphoma (NHL) seen in both children and adults. While it is the most common non-anaplastic mature T-cell lymphoma of childhood, it is quite rare and therefore, the standard of care remains largely undefined. It is a disease characterized by clinical and pathological heterogeneity and is generally associated with an aggressive clinical course and poor prognosis in adults. Retrospective reports on treatment outcomes for pediatric PTCL-NOS are limited by small cohorts, variable clinical presentations, and heterogeneous treatment regimens. Though published survival rates in children appear encouraging compared to those from prospective studies in adults, the prognosis is guarded, and relatively low curative outcomes are in stark contrast to more common pediatric NHL. While recent landmark gene profiling studies have shed light on the molecular landscape of the disease in adults-identifying molecular subgroups with prognostic significance-the biology of PTCL-NOS remains unclear in children. Here we review the clinical presentation and diagnosis, historical treatment approaches, current knowledge of the disease biology and the role of hematopoietic stem cell transplant (HSCT) in PTCL-NOS in children to pursue a better understanding of this heterogenous condition and empower physicians to use this information to best support our pediatric population. Studies focusing on pediatric PTCL-NOS are required to unravel the disease biology in children, improve risk stratification, and better define upfront treatment through the role of targeted agents and HSCT, as we look to future directions of the care of children with PTCL-NOS.