Mast cell leukemia

Mast cell leukemia is an extremely aggressive subtype of acute myeloid leukemia that usually occurs de novo but can, rarely, evolve from transformation of chronic myeloid leukemia into the more aggressive acute myeloid leukemia. In a small proportion of cases, acute mast cell leukemia may evolve from a more progressive form of systemic mastocytosis. In addition to meeting the diagnostic criteria for systemic mastocytosis, diagnosis of acute mast cell leukemia by the WHO criteria includes the requirement for a prevalence of 20% neoplastic mast cells in marrow. MCL can be further classified as leukemic (at least 10% atypical immature circulating mast cells in peripheral blood) or aleukemic (less than 10% circulating MCs) but the importance of this distinction is debated, and this indicator is no longer required for diagnosis.