Proposed WHO-based nested classification of malignant lymphoid neoplasms. (A) Proposed WHO-based nested classification of malignant lymphoid neoplasms for epidemiologic research. (B) Proposed WHO-based nested classification of malignant lymphoid neoplasms: mature B-cell subtypes. (C) Proposed WHO-based nested classification of malignant lymphoid neoplasms: mature T-cell subtypes.