Cytopenia in one or more hematopoietic cell lineages that remains unexplained following thorough evaluation. The hematopoietic cell dysplasia is mild and does not fulfill the criteria for myelodysplastic syndrome, but the cytopenia may be severe. There is no evidence of clonal hematopoiesis or the variant allele frequency (VAF) is less that 2 percent. There is no other evidence of hematologic malignancy. It may progress to an overt myelodysplastic syndrome or other myeloid neoplasms such as acute myeloid leukemia, myeloproliferative neoplasm, or mast cell disorder. [from
NCI]