Peripheral T-cell lymphoma not otherwise specified

Peripheral T-cell lymphoma (PTCL) not otherwise specified (NOS) is a heterogeneous group of diseases, where all the not otherwise classifiable mature T-cell lymphomas are grouped. In this chapter, the authors review the clinical characteristics and underlying biology of PTCL-NOS with a focus on their potential clinical implications. They also briefly discuss advances in management both in the frontline and relapsed setting. The Prognostic Index, a prognostic tool specifically designed for PTCL-NOS, was able to discriminate between four risk groups: no adverse prognostic factors (group 1), one (group 2), two (group 3) or three to four (group 4) adverse prognostic factors. The limitations of effective therapies, both at the frontline and the relapsed setting in PTCL, highlight the need for more mechanistic therapeutic approaches. The future is clearly in developing combination therapies that are rationally chosen based on disease biology.