WHO Criteria (Systemic Mastocytosis)
Applies the WHO criteria for systemic mastocytosis: one major plus one minor, or three minor.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Multifocal dense infiltrates
- Yes
- Activating KIT mutation
- Yes
- Measured baseline tryptase, ng/mL
- 30
- Extra alpha-tryptase gene copies
- 1
Result: Systemic mastocytosis criteria met
The tool opens with these values already filled in. Replace them with your own.
What the result means
- The rule
- One major criterion plus one minor criterion, or three minor criteria.
- Major
- Multifocal dense infiltrates of mast cells, 15 or more in aggregates, in bone marrow or another extracutaneous organ.
- Minor 1
- More than 25 percent of mast cells atypical or spindle-shaped.
- Minor 2
- An activating KIT point mutation at codon 816 or another critical region.
- Minor 3
- Mast cells aberrantly expressing CD2, CD25 or CD30. CD30 was admitted in the 2022 edition.
- Minor 4
- Baseline serum tryptase above 20 ng/mL, only in the absence of an associated myeloid neoplasm.
- The correction
- In hereditary alpha-tryptasemia, divide the tryptase by 1 plus the EXTRA alpha-tryptase gene copies first. 30 ng/mL with one extra copy corrects to 15 and does NOT meet the criterion.
- Why it matters
- Where three minor criteria carry the diagnosis, that one item is the difference between systemic and cutaneous mastocytosis.
What you enter
- Multifocal dense infiltrates
- Atypical morphology above 25 percent
- Activating KIT mutation
- Aberrant CD2, CD25 or CD30
- Measured baseline tryptase, ng/mL
- Extra alpha-tryptase gene copies
- Associated myeloid neoplasm present
How this is calculated
Khoury JD, Solary E, Abla O, et al. The 5th edition of the WHO Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms. Leukemia. 2022;36(7):1703-1719. Tryptase correction: Valent P, Akin C, Hartmann K, et al, consensus proposal. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.