BCL6 and mature T-cell and NK-cell non-Hodgkin lymphoma: The 2016 WHO revision and subsequent 5th edition emphasize the concept of a T-follicular helper (TFH) lineage for AITL and a subset of PTCL-NOS, defined by variable expression of PD-1, ICOS, CXCR5, CD10, and/or BCL6.