WHO diagnostic criteria (2008) for systemic mastocytosis
| Criteria . |
|---|
| Major |
| Multifocal, dense infiltrates of MC (≥ 15 MC in aggregates) in BM and/or other extracutaneous organ(s) |
| Minor |
| (1) > 25% of MC in the infiltrate of biopsy sections are spindle-shaped or have atypical morphology or, of all MC in the BM aspirate smears, > 25% are immature or atypical |
| (2) Activating point mutation at codon 816 of c-KIT in BM, blood, or another extracutaneous organ |
| (3) MC in BM, blood, or extracutaneous organs express CD2 and/or CD25 in addition to normal MC markers |
| (4) Total serum tryptase persistently exceeds 20 ng/mL* |
| Criteria . |
|---|
| Major |
| Multifocal, dense infiltrates of MC (≥ 15 MC in aggregates) in BM and/or other extracutaneous organ(s) |
| Minor |
| (1) > 25% of MC in the infiltrate of biopsy sections are spindle-shaped or have atypical morphology or, of all MC in the BM aspirate smears, > 25% are immature or atypical |
| (2) Activating point mutation at codon 816 of c-KIT in BM, blood, or another extracutaneous organ |
| (3) MC in BM, blood, or extracutaneous organs express CD2 and/or CD25 in addition to normal MC markers |
| (4) Total serum tryptase persistently exceeds 20 ng/mL* |
Diagnosis of systemic mastocytosis requires the presence of the major criterion and 1 minor criterion or at least 3 minor criteria.
MC indicates mast cell; and BM, bone marrow.
Serum tryptase is not valid as a criterion if there is an associated clonal myeloid disorder.