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Haematology · Allergy and Immunology

ICC 2022 Diagnostic Criteria for Systemic Mastocytosis calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Tyrosine kinase fusion of the eosinophilia family

A tyrosine kinase fusion that places the disease in myeloid or lymphoid neoplasm with eosinophilia excludes systemic mastocytosis.

Major criterion: dense mast-cell aggregates

Multifocal dense infiltrates of tryptase-positive and/or CD117-positive mast cells, at least 15 cells in aggregates, in marrow or another extracutaneous organ.

More than 25% spindle-shaped or atypical mast cells

More than 25% of mast cells on the biopsy are spindle-shaped or atypical and immature.

Mast cells express CD25, CD2, or CD30 plus usual mast-cell markers

This minor criterion is expression of CD25, CD2, and/or CD30 together with usual mast-cell markers.

Activating KIT mutation

KIT D816V or another activating KIT mutation is one minor criterion.

ng/mL

Allowed range: 0–1000 ng/mL

Quick picks

Persistently above 20 ng/mL is one minor criterion. A value of 20 is not. It does not count when an associated myeloid neoplasm is present.

Associated myeloid neoplasm

When systemic mastocytosis occurs with an associated myeloid neoplasm, serum tryptase does not count as a minor criterion.

Result

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Clinical inputs

  • Tyrosine kinase fusion of the eosinophilia family
  • Major criterion: dense mast-cell aggregates
  • More than 25% spindle-shaped or atypical mast cells
  • Mast cells express CD25, CD2, or CD30 plus usual mast-cell markers
  • Activating KIT mutation
  • Serum tryptase (ng/mL)Accepted range: 0 to 1000
  • Associated myeloid neoplasm

Primary source

Arber DA et al. International Consensus Classification of Myeloid Neoplasms and Acute Leukemias: integrating morphologic, clinical, and genomic data. Blood. DOI: 10.1182/blood.2022015850. PMID: 35767897. Table 11: the major criterion is multifocal dense infiltrates of tryptase- and/or CD117-positive mast cells, at least 15 mast cells in aggregates, in bone marrow and/or another extracutaneous organ. Without the major criterion, at least 3 of 4 minor criteria are required: more than 25% spindle-shaped or atypical immature mast cells in the biopsy, mast cells expressing CD25, CD2, and/or CD30 plus usual mast-cell markers, a KIT D816V or other activating KIT mutation, and serum tryptase persistently above 20 ng/mL. Tryptase does not count as a minor criterion in SM with an associated myeloid neoplasm. A myeloid/lymphoid neoplasm with eosinophilia tyrosine kinase fusion excludes systemic mastocytosis only when a KIT mutation is absent. When a KIT mutation is present, the fusion is the associated myeloid neoplasm and the mastocytosis criteria still apply. (2022)

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