CD274 and thyroiditis: In contrast, thyroid MALT lymphomas show highly frequent and concurrent inactivating mutations in TET2, CD274 and TNFRSF14.48,57 CD274 (PD-L1) and TNFRSF14 are ligands for co-inhibitory receptor PD1 and BTLA on T-helper cells, respectively, and their inactivation may indirectly promote T-cell help to malignant B cells, thus contributing to lymphomagenesis.57