Major:

 Multifocal dense infiltrates of mast cells (>15 mast cells per aggregate) in bone marrow or other extracutaneous tissues

Minor:

 Abnormal mast cell morphology (spindle shape, bi- or multi-lobed or eccentric nucleus, hypogranulated cytoplasm)

 Aberrant mast cell surface phenotype with expression of CD25 (IL-2 receptor alpha chain) and/or CD2

 Detection of codon 816 mutation in peripheral blood cells, bone marrow cells, or an extracutaneous lesional tissue

 Total serum tryptase >20 ng/mL