Criteria of WHO for systemic mastocytosis [4]. Systemic mastocytosis can be diagnosed if one major and one minor or three minor criteria are met.

Table 1: Criteria of WHO for systemic mastocytosis [4]. Systemic mastocytosis can be diagnosed if one major and one minor or three minor criteria are met.

Major Criteria
Multifocal, dense aggregates of mast cells (15 or more) in bone marrow sections and confirmed by tryptase immunohistochemistry or other special stains.
Major Criteria
1. More than 25% of the MC in the infiltrate in biopsy section have atypical morphology, or, of all the mast cells in the aspirate smear	2. Mast cells co-express CD117 with CD2 and/or CD25;	3. Detection of KIT D816V mutation in bone marrow, blood, or other extracutaneous organs	4. Serum total tryptase persistently > 20 ng/ml.