ToolsCalculators
International Consensus Classification (ICC) Diagnostic Criteria for Systemic Mastocytosis
Applies the ICC major/minor criteria to determine whether systemic mastocytosis is diagnosed.
International Consensus Classification (ICC) Diagnostic Criteria for Systemic Mastocytosis
Major criterion: multifocal dense infiltrates of mast cells (aggregates of >=15 mast cells) in bone marrow biopsy and/or another extracutaneous organ
Minor: atypical (e.g., spindle-shaped) mast cell morphology in >25% of mast cells on bone marrow smear/biopsy, or immature/atypical mast cells
Minor: KIT-activating point mutation at codon 816 (e.g., D816V) or another activating KIT mutation, in bone marrow, blood, or another extracutaneous organ
Minor: mast cells in bone marrow, blood, or another extracutaneous organ express CD25 and/or CD2 and/or CD30 in addition to normal mast cell markers
Minor: baseline serum tryptase persistently >20 ng/mL (not attributable to an associated myeloid neoplasm or hereditary alpha-tryptasemia)
ResultCriteria not met
Diagnostic criteria for systemic mastocytosis are not fulfilled with the findings entered.
- Major criterion met
- No
- Minor criteria met
- 0/4
When to use
- Working up suspected systemic mastocytosis (e.g., unexplained anaphylaxis, elevated baseline tryptase, cytopenias, or skin lesions of mastocytosis) after bone marrow biopsy and ancillary studies have been obtained.
Formula
Systemic mastocytosis is diagnosed if the major criterion (multifocal mast cell aggregates, >=15 cells, in bone marrow and/or an extracutaneous organ) plus >=1 minor criterion are present, OR if >=3 minor criteria are present in the absence of the major criterion. Minor criteria: atypical mast cell morphology; KIT-activating mutation; aberrant CD25/CD2/CD30 expression; serum tryptase persistently >20 ng/mL.
Pearls and pitfalls
- The ICC (2022) broadened the KIT-mutation minor criterion beyond D816V to include any activating KIT mutation, and added CD30 as an accepted aberrant marker alongside CD25/CD2.
- Skin lesions typical of cutaneous mastocytosis are not required for a diagnosis of systemic mastocytosis and do not substitute for the bone-marrow-based criteria.