Multifocal, dense infiltrates of mast cells (≥15 mast cells in
aggregates) detected on bone marrow biopsy and/or on extracutaneous
organs biopsy |
>25% of mast cells in the infiltrate are
spindle-shaped or have atypical morphology on bone marrow/
extracutaneous organs biopsy OR >25% of mast cells in bone
marrow aspirate are immature or atypical |