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Table 156-2

Diagnostic Criteria for Systemic Mastocytosisa

Major: Multifocal dense infiltrates of mast cells in bone marrow or other extracutaneous tissues with confirmation by immunodetection of tryptase or metachromasia
Minor: Abnormal mast cell morphology with a spindle shape and/or multilobed or eccentric nucleus
Aberrant mast cell surface phenotype with expression of CD25 and CD2 (IL-2 receptor) in addition to C117 (c-kit)
Detection of codon 816 mutation in peripheral blood cells, bone marrow cells, or lesional tissue
Total serum tryptase (mostly alpha) >20 ng/mL

aDiagnosis requires either the major and one minor or three minor criteria.