ToolsCalculators
World Health Organization (WHO) Diagnostic Criteria for Systemic Mastocytosis
Major/minor criteria for diagnosing systemic mastocytosis on bone marrow or extracutaneous biopsy.
World Health Organization (WHO) Diagnostic Criteria for Systemic Mastocytosis
Major: multifocal dense mast cell infiltrates (>=15 mast cells in aggregates) in bone marrow and/or another extracutaneous organ
Minor: >25% of mast cells are spindle-shaped/atypical on biopsy, or >25% are immature/atypical on bone marrow aspirate smears
Minor: activating KIT mutation at codon 816 (or elsewhere) detected in bone marrow, blood, or another extracutaneous organ
Minor: mast cells aberrantly express CD2, CD25, and/or CD30 in bone marrow, blood, or another extracutaneous organ
Minor: baseline serum total tryptase persistently >20 ng/mL
Not a valid criterion if there is an associated clonal haematologic non-mast-cell lineage disease.
ResultDoes not meet WHO criteria for systemic mastocytosis
Diagnostic criteria not satisfied with the findings entered. Systemic mastocytosis requires the major criterion plus >=1 minor criterion, or >=3 minor criteria.
- Major criterion met
- No
- Minor criteria met
- 0 / 4
When to use
- Establishing a tissue diagnosis of systemic mastocytosis in a patient with suspected mast cell disease undergoing bone marrow (or other extracutaneous organ) evaluation.
Formula
Systemic mastocytosis is diagnosed when the major criterion (multifocal dense mast cell infiltrates, >=15 mast cells in aggregates, in bone marrow and/or another extracutaneous organ) plus >=1 of 4 minor criteria are present, OR when >=3 of the 4 minor criteria are present without the major criterion.
Pearls and pitfalls
- CD30 was added to the aberrant mast cell marker minor criterion in the 2016 WHO revision, alongside the earlier CD2/CD25.
- The elevated-tryptase minor criterion is not applicable when there is an associated haematologic neoplasm driving tryptase elevation independent of mast cell disease.