Table III.

Diagnostic criteria for SM according to WHO recommendations [18]

Major

Multifocal dense infiltrates of MC in the bone marrow or other extracutaneous organs, confirmed by special stains such as MC tryptase (>15 MC aggregating)

Minor

In MC infiltrates in the bone marrow or other Extracutaneous organs, >25% of MC are spindle-shaped Or otherwise atypical; or in bone marrow smears, >25% of MC are spindle shaped or otherwise atypical

Activating point mutation of KIT in codon 816 is present in extracutaneous organs

MCs in extracutaneous organs (CD117) co-express either CD2 or CD25, or both, as determined by flow cytometry

Serum tryptase is persistently >20 ng/ml (does not count in patients who have an associated clonal haematological non-MC disease; AHNMD)