| Proposed entity | Definition |
| Idiopathic cytopenia of undetermined significance (ICUS) | Single or multiple blood cytopenias that remain unexplained despite appropriate evaluation including marrow examination. If present, dysplasia is not prominent (<10% of cells per lineage). Patients with ICUS are not known to have a clonal disorder either because no clonality testing has been performed or because testing was performed but the assay did not reveal a clonal mutation. |
| Clonal hematopoiesis of indeterminate potential (CHIP) | Identification of a clonal mutation associated with hematologic neoplasia in an individual who does not yet meet WHO criteria for diagnosis of a hematologic neoplasm. Individuals with CHIP usually have normal complete blood counts, normal erythrocyte indices or mild red cell macrocytosis without anemia, or minimal and clinically insignificant cytopenias. If present, dysplasia is not prominent (<10% of cells per lineage). |
| Clonal cytopenia of undetermined significance (CCUS) | Patients who have clinically meaningful unexplained cytopenias (ICUS) and are also found to have a clonal mutation, yet meet no other WHO-defined criteria for MDS or another hematologic neoplasm. |
