. 2016 Dec;16(6):580–583. doi: 10.7861/clinmedicine.16-6-580

Table 1.

WHO diagnostic criteria for systemic mastocytosis

Major criterion	Minor criteria
Multifocal, dense aggregates of mast cells (15 or more) detected in sections of bone marrow and confirmed by tryptase immunohistochemistry or other special stains	In biopsy section, more than 25% of the masts cells in the infiltrate have atypical morphology, or, of all the mast cells in the aspirate smear, more than 25% are immature or atypical Mast cells co-express CD117 with CD2 and/or CD25 Detection of KIT point mutation at codon 816 in bone marrow, blood, or other extracutaneous organs Serum total tryptase persistently >20 ng/mL (not a valid criteria in cases of systemic mastocytosis with associated clonal hematologic non-mast-cell lineage disease)
Diagnosis may be made if one major plus one minor, or three minor criteria are fulfilled

Major criterion

Minor criteria

Multifocal, dense aggregates of mast cells (15 or more) detected in sections of bone marrow and confirmed by tryptase immunohistochemistry or other special stains

In biopsy section, more than 25% of the masts cells in the infiltrate have atypical morphology, or, of all the mast cells in the aspirate smear, more than 25% are immature or atypical
Mast cells co-express CD117 with CD2 and/or CD25
Detection of KIT point mutation at codon 816 in bone marrow, blood, or other extracutaneous organs
Serum total tryptase persistently >20 ng/mL (not a valid criteria in cases of systemic mastocytosis with associated clonal hematologic non-mast-cell lineage disease)

Diagnosis may be made if one major plus one minor, or three minor criteria are fulfilled

Reproduced from Valent et al.²