S1PR2 and diffuse large B-cell lymphoma: The TdT‐positive DLBCL/HGBCL‐MYC/BCL2 group was characterised by the mutation signature associated with FL (BCL2, KMT2D, CREBBP, TNFRSF14), and those associated with high‐grade transformation (MYC, TP53, CCND3, PIM1, B2M, DDX3X, S1PR2).