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9 - Grade/differentiation unknown, not stated, or not applicable
M3 Module 5: PH9
Criteria for systemic mastocytosis met, and bone marrow aspirate shows 20% or more of cells are mast cells or 10% or more mast cells seen in circulating blood, shape of mast cells and nuclei have malignant features. No associated clonal hematologic non-mast cell disease. Aleukemic mast cell leukemia is a rare variant where <10% of circulating nucleated cells are mast cells.
Acute mast cell leukemia is a rapidly progressive disorder with leukemic mast cells in blood and in large numbers in marrow. Mast cells must equal or exceed 20% of all nucleated cells in bone marrow aspirate smears. Bone marrow will show a diffuse, compact infiltrate of mast cells with a marked reduction of normal precursor blood cells and fat cells. The common signs and symptoms include fever, headache, flushing of face and trunk. Symptoms include abdominal pain, bone pain, and peptic ulcer which are more prevalent than in other subtypes of acute myeloid leukemia. These former symptoms are due to release of a substance called histamine from neoplastic mast cells. Enlargement of the liver and spleen, or hepatosplenomegaly is characteristic. The mast cells also release many anticoagulants like heparin which can lead to serious bleeding. Liver and splenic dysfunction also contribute to hemorrhage
Definitive Diagnostic Methods
Bone marrow biopsy
Somatic point mutation at codon 816 in kit receptor gene
Immunohistochemical markers anti-tryptase and anti-CD117