(1) A T follicular helper (TFH) cell phenotype, as defined by the expression of at least two (ideallythree) of the following markers: CD10, BCL6, PD1, CXCL13, CXCR5, ICOS, and SAP (2) Exclusion from any of the specifically defined entities of mature T-cell lymphoma in the current classification. Here, ICOS is linked to T-cell non-Hodgkin lymphoma.