Table 1.

Diagnostic criteria of systemic mastocytosis (SM) and monoclonal mast cell activation syndrome (MMAS) (adapted from references: [11,18,31,32]). Altogether, there is one major criterion and four minor criteria.

SM	Diagnosis is confirmed if patient expresses one major criterion and one minor criterion or expresses three minor criteria in extracutaneous organ biopsy specimens
Major criterion Minor criteria	Multifocal aggregates of MCs (≥15 MCs per cluster) in biopsy sections In MC infiltrates in extracutaneous biopsy sections, >25% of the MCs (CD117+) are spindle-shaped or have atypical morphology Presence of an activating KIT mutation at codon 816, generally D816V, in bone marrow, blood, or other extracutaneous organ(s) Detection of aberrant MC clones expressing CD117 with CD25 and/or CD2 and/or CD30 in bone marrow or blood or another extracutaneous organ(s) Baseline serum tryptase persistently exceeds ≥20 ng/mL
MMAS	Diagnosis requires presence of one or two minor criteria of SM
	Presence of an activating KIT mutation D816V, in bone marrow, blood or other extracutaneous organ(s) AND/OR 2.Detection of aberrant MC clones expressing CD117 with CD25 and/or CD2 and/or CD30 in bone marrow or blood or another extracutaneous organ(s)