Diagnostic criteria Mastocytosis

Diagnostic criteria:
Major:  – Multifocal dense infiltrates of MCs (≥15 MCs in aggregates) in BM biopsies and/or in sections of other extracutaneous organ(s)
Minor: – >25% of all MCs are atypical cells type I (hypogranulation, oval and eccentric nuclei), type II (nuclei are bilobed or polylobed) or are spindle-shaped.
             – KIT point mutation at codon 816 in the BM or another extracutaneous organ.
             – MCs express CD2 and/or CD25.
             – Baseline serum tryptase level >20 ng/mL (in case of an unrelated myeloid neoplasm, this item is not valid as an SM criterion).
Criteria for diagnosis of Systemic Mastocytosis are: 1 major and 1 minor or 3 minor SM criteria.
WHO mastocytosis classification
1. Cutaneous mastocytosis (CM)
2. Systemic mastocytosis
    a. Indolent systemic mastocytosis (ISM)
    b. Smoldering systemic mastocytosis (SSM)
    c. Systemic mastocytosis with an associated hematological neoplasm (SM-AHN)
    d. Aggressive systemic mastocytosis (ASM)
    e. Mast cell leukemia (MCL)
3. Mast cell sarcoma (MCS)