Unclassifiable Myelodysplastic/Myeloproliferative Neoplasms (MDS/MPN-U)

Definition

Myeloid neoplasm with both dysplastic and myeloproliferative features, which does not show specific disease-defining cytogenetic abnormalities and does not now or on previous biopsies satisfy criteria of a defined myeloid neoplasm

Myelodysplastic and myeloproliferative features are BOTH REQUIRED
- Presence of dysplastic features sufficient for an MDS diagnosis
- Prominent myeloproliferative features
  - e.g. prominent thrombocytosis with megakaryocytic proliferation, prominent leukocytosis, etc
Must not satisfy criteria for any defined myeloid neoplasm
- Peripheral blood and bone marrow blasts <20%
- No evidence of disease-defining cytogenetic abnormalities
  - e.g. BCR/ABL1 translocations, isolated 5q minus, inv(3q21q26) or t(3;3)(q21;q26), acute myeloid leukemia-defining abnormalities inv(16), t(8;21)
No prior history of a defined myeloid neoplasm
No recent cytotoxic or growth factor therapy which may obscure diagnostic features
Includes new and provisional entities (see individual descriptions):
- Refractory anemia with ring sideroblasts associated with marked thrombocytosis (RARS-T, provisional category in WHO 2008)
- MDS/MPN with isolated isochromosome 17q (new, not specifically categorized in WHO 2008)

Dita Gratzinger MD PhD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting: 11/6/11