Table 9

WHO classification of mastocytosis

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)
  • * These subtypes require information regarding B and C findings for complete diagnosis,20 all of which may not be available at the time of initial tissue diagnosis.

  • This category is equivalent to the previously described “systemic mastocytosis with an associated clonal hematological non-mast cell lineage disease (SM-AHNMD).” AHNMD and AHN can be used synonymously.