Table 2.

Types and subtypes of mastocytosis per 2022 ICC [9,33] and WHO 5th edition ^# [10,49].

	2022 ICC	WHO 5th Edition
CM	Maculopapular CM (MPCM; previously known as urticaria pigmentosa) Monomorphic Polymorphic	Urticaria pigmentosa/Maculopapular CM Monomorphic Polymorphic
	Diffuse CM (DCM)	Diffuse CM
	Mastocytoma of the skin *	Cutaneous mastocytoma Isolated mastocytoma Multilocalized mastocytoma
SM	Indolent SM (Includes bone marrow mastocytosis **)	Bone marrow mastocytosis **
		Indolent SM
	Smoldering SM	Smoldering SM
	Aggressive SM	Aggressive SM
	SM with an associated myeloid neoplasm	SM with an associated hematologic neoplasm
	Mast cell leukemia	Mast cell leukemia
MCS	Mast cell sarcoma	Mast cell sarcoma

^# Well-differentiated systemic mastocytosis (WDSM) represents a morphologic variant that may occur in any SM type/subtype, including mast cell leukemia [49,50]. * In case of ≥ 4 lesions, a diagnosis of MPCM is favored over mastocytoma by 2022 ICC [33]. ** The 5th WHO recognizes BMM as an independent SM subcategory, while the 2022 ICC considers BMM a variant of indolent SM (ISM).